SERV1789 October 2004
SERVICE TRAINING TECHNICAL PRESENTATION
D8T TRACK-TYPE TRACTOR
Meeting Guide 789 (STMG)
D8T TRACK-TYPE TRACTOR MEETING GUIDE 789
SLIDES AND SCRIPT AUDIENCE
Level II Service personnel who have knowledge of the principles of machine systems operation, diagnostic equipment, and procedures for testing and adjusting.
CONTENT This presentation discusses the operation of the power train, the differential steering system, the implement hydraulic system, the demand fan and the cooling systems, and the Caterpillar Monitoring and Display System with Advisor™ on the D8T Track-type Tractor. Also discussed is the operation of the controls in the operator compartment and the location and identification of the major components of the C15 ACERT™ technology engine.
OBJECTIVES After learning the information in this presentation, the serviceman will be able to: 1. locate and identify all of the major machine components; 2. locate and identify all filters, dipsticks, indicators, fill tubes, drains and test points; 3. locate and identify the major components of the C15 ACERT™ technology engine and trace the flow of fuel through the C15 engine fuel delivery system; 4. trace the flow of air through the engine's air intake system; 5. trace the flow of coolant through the cooling system of the D8T; 6. identify and explain the function/operation of each component in the hydraulic demand fan system; 7. trace the flow of oil through the hydraulic demand fan system; 8. identify and explain the function/operation of each component in the power train system; 9. trace the flow of oil through the power train hydraulic system; 10. identify and explain the function/operation of each component in the steering hydraulic system; 11. trace the flow of oil through the steering hydraulic system; 12. explain the function/operation of each component in the implement hydraulic system; 13. trace the flow of oil through the implement hydraulic system; and 14. locate and identify all the major components in the Caterpillar Monitoring and Display System, with Advisor.
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REFERENCES Engine Systems Operation, Testing & Adjusting (C15 &C18 Engine) . . . . . . . . . . . . .SENR9382 Engine Troubleshooting Guide (C15 &C18 Engine) . . . . . . . . . . . . . . . . . . . . . . . . . .SENR9748 Systems Operation, Testing & Adjusting (Power Train) . . . . . . . . . . . . . . . . . . . . . . .RENR7526 Systems Operation, Testing & Adjusting (Hydraulic System) . . . . . . . . . . . . . . . . . . .RENR7527 Systems Operation, Testing & Adjusting (Cooling Systems) . . . . . . . . . . . . . . . . . . . .RENR8197 Schematic (Hydraulic System) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .RENR7528 Schematic (Electrical) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .RENR7530
PREREQUISITES Interactive Video Course "Fundamentals of Mobile Hydraulics" . . . . . . . . . . . . . . . .TEMV9001 Interactive Video Course "Fundamentals of Electrical Systems" . . . . . . . . . . . . . . . .TEMV9002 STMG 546 "Graphic Fluid Power Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .SESV1546
SUPPLEMENTARY TRAINING MATERIALS D8T Track-type Tractor - New Product Introduction (NPI) . . . . . . . . . . . . . . . . . . .SERV7104-09 STMG 790 "Caterpillar Monitoring and Display System, with Advisor" . . . . . . . . . . .SERV1790 STMG 736 "D8R Series II Track-type Tractor" . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .SESV1736 STMG 633 "D8N Track-type Tractor - Two Pump Hydraulic System" . . . . . . . . . . . .SERV1633 STMG 547 "Track-type tractor - Power Train and Implements" . . . . . . . . . . . . . . . . . .SERV1547 Technical Instruction Module "Air Conditioning Principles and Operation" . . . . . . . .SEGV2580 CD ROM version of SEGV2580 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .SERV2580 Technical Instruction Module "Air Conditioning Service Procedures" . . . . . . . . . . . . .SERV2581 Estimated Time: 6 Hours Visuals: 145 Slides Serviceman Handouts: 5 Lab Exercises Form: SERV1789 Date: 10/04
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TABLE OF CONTENTS INTRODUCTION ........................................................................................................................5 OPERATOR'S COMPARTMENT................................................................................................6 CATERPILLAR MONITORING AND DISPLAY SYSTEM WITH ADVISOR™ .................21 Start Up .................................................................................................................................28 ENGINE......................................................................................................................................33 Fuel System...........................................................................................................................52 Engine Air System ................................................................................................................53 Cooling System.....................................................................................................................54 Hydraulic Demand Fan System ............................................................................................58 POWER TRAIN .........................................................................................................................66 Power Train Electronic Control System ...............................................................................67 Power Train Hydraulic System .............................................................................................68 Torque Divider ......................................................................................................................75 Power Shift Transmission .....................................................................................................84 Electronic Brake Control Valve ............................................................................................90 DIFFERENTIAL STEER MECHANICAL OPERATION ......................................................101 Differential Steering System Operation..............................................................................103 IMPLEMENT HYDRAULIC SYSTEM ..................................................................................118 Implement System Operation .............................................................................................129 Implement Pump Operation................................................................................................131 Implement Control Valve operation....................................................................................142 Dual Tilt Operation .............................................................................................................153 Quick-drop Valve ................................................................................................................159 AutoCarry Components ......................................................................................................166 CONCLUSION.........................................................................................................................173 HYDRAULIC SCHEMATIC COLOR CODE.........................................................................174 VISUAL LIST ..........................................................................................................................175 SERVICEMAN'S HANDOUTS...............................................................................................177
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D8T TRACK-TYPE TRACT OR
© 2004 Caterpillar Inc. 1
INTRODUCTION This presentation discusses the major design features and changes, the component locations and identifications, and the systems operation of the D8T Track-type Tractor. The D8T appearance is similar to the D8R Series II. The operator station incorporates the common cab, which is also used for the D9T, and the D10T Track-type Tractors. The D8T is powered by the C15 ACERT™ (Advanced Combustion Emissions Reduction Technology) electronic engine equipped with the Mechanical Electronic Unit Injection (MEUI) fuel system. This engine also utilizes the A4 ECM engine control and is equipped with an Air To Air AfterCooler (ATAAC) intake air cooling system. The C15 is an in-line six-cylinder arrangement and is rated at 231.6 net kW (310 net horsepower) at 1850 rpm. Other standard features include: power train hydraulic system with a common top pressure strategy and remote pressure test ports, an electro-hydraulic demand fan, electro-hydraulic steering, an electro-hydraulic implement system with easily accessible components, the Advanced MOdular Cooling System (AMOCS) radiator, and the new Caterpillar Monitoring and Display System with Advisor™. The D8T can also be equipped with optional attachments such as an engine pre-lubrication system, a cold-start package, a reversing fan, dual tilt blade controls with the Automatic Blade Assist (ABA) feature, and AutoCarry. The D8T can be ordered ready to accept the Computer Aided Earthmoving System (CAES) and the AccuGrade system. The serial number prefix for the D8T is KPZ, for machines built in the U.S. The serial number prefix for the D8T built in Brazil is J8B.
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2 OPERATOR'S COMPARTMENT The operator's compartment for the D8T incorporates the "Common Cab," which is used on the D8T, the D9T, and the D10T Track-type Tractors. The cab is eight inches wider than the cab used for previous models. The cab has wider doors that open 20° further for easier entry and exit. It contains more glass area for better overall visibility for the operator. Included in the new cab design is: - the Caterpillar Monitoring and Display System with Advisor; - a new dash with an automotive style sealed instrument cluster; - a new right-hand console with redesigned controls for lighting and other machine systems; and - electro-hydraulic implement and steering controls.
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3 The Cat contour seat is standard equipment, with air suspension available as an attachment. The seat provides maximum comfort and less operator fatigue. The operator can adjust the seat height, the front to rear seat position and tilt, and the seat back angle. The seat is angled 15° to the right in order to provide maximum visibility of implement operation. The padded left armrest is manually adjustable for height using the two knobs (1) below the armrest The padded right armrest is similarly adjustable. Padded knee braces (2) provide operator comfort when operating the machine on side slopes. The back and seat cushion assembly can be removed from the suspension base by removing one 8mm bolt (3), located on the lower front, center of the seat.
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4 Forward of the left armrest is the steering control lever, or tiller (1). The steering tiller combines steering, directional changes, and gear selection into one control. When pulled up, the parking brake switch (2) shifts the transmission to FIRST gear NEUTRAL and energizes the parking brake and secondary brake solenoids on the electronic brake valve, which engages the brakes. The parking brake switch also electronically disables the steering system and mechanically locks the tiller housing. FORWARD, NEUTRAL, and REVERSE are controlled by rotating the tiller hand grip (3). All three positions have detents that hold the tiller in the selected position. A PWM rotary position sensor connected to the hand grip provides a signal to the Power Train ECM when the handgrip is rotated. In addition, a forward switch and a reverse switch are also used to signal the Power Train ECM and confirm the hand grip position. The Power Train ECM then sends a corresponding signal to the appropriate transmission modulating solenoid valves to engage and disengage the forward and reverse clutches in the transmission. The top yellow button (4) upshifts the transmission one gear range at a time, and the bottom yellow button (5) downshifts the transmission one gear range at a time.
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Left turns are accomplished by rotating the tiller (1) toward the front. Right turns are accomplished by rotating the tiller toward the rear. When the operator releases the tiller, a centering spring returns the tiller to the center (NO STEER) position. Three PWM rotary position sensors (triple redundant) are attached to the tiller shaft and send electronic signals to the Power Train ECM regarding the tiller's position. The Power Train ECM sends a corresponding signal to the left or right proportional solenoid valves that control the steering pump. NOTE: The differential steering strategy still incorporates the standard "S-Turn" logic used in previous differential steer machines. NOTE: When the parking brake is engaged, the secondary brake solenoid is also energized, as a backup measure.
WARNING
With the engine running and the transmission shifted to NEUTRAL, rotating the steering tiller toward the front or the rear will cause the machine to steer. The tracks will counterrotate, resulting in the machine pivoting about its center point. To avoid personal injury and/or property damage, always ENGAGE the parking brake when not operating the machine and when other personnel are nearby.
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5 The right console contains the implement controls and most of the controls and switches for machine systems and functions. The dozer control lever (1) allows the operator to control all of the blade functions with one lever. To the rear of the dozer control lever is the ripper control handle (2). The ripper control handle allows the operator to control all of the ripper functions. If the machine is equipped with a winch, the winch control would be located in this same position. Located to the rear of the ripper handle and on the vertical panel of the right console is the rear action lamp (3), which alerts the operator of a machine system that is operating out of its normal range. Just forward of the action lamp is a 12-volt switched power adapter (4). To the right of the dozer control lever is the forward horn button (5). On the vertical panel and above the forward horn button, is the key start switch (6). Ahead of the dozer control lever is the Cat Advisor™ graphical display module (7), which will be discussed in greater detail, later in this presentation. The Machine Security System (MSS) indicator light (8) is located below the Advisor panel.
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6 The dozer control lever (1) allows the operator to control all of the blade functions with one lever. When the lever is moved FORWARD, the blade will LOWER. Moving the lever forward to a point within 3°- 4° of the soft FLOAT detent causes the quick-drop valve to activate. Moving the lever completely forward to the soft FLOAT detent activates the FLOAT function. The lever will return to the centered position and maintain the FLOAT function. Moving the lever either forward or rearward from the centered position will deactivate the FLOAT function. Moving the lever to the rear of the center (HOLD) position causes the blade to RAISE. Moving the dozer control lever to the right tilts the right side of the blade down. Moving the lever to the left tilts the left side of the blade down. If the machine is equipped with dual tilt, moving the thumb lever (2) to the right allows the operator to DUMP the blade (PITCH FORWARD). Moving the thumb lever to the left will RACK BACK the blade. The left yellow button (3) allows the operator to activate segments in the Auto Blade Assist (ABA) cycle and/or the AutoCarry cycle, if the machine is equipped with ABA or AutoCarry. The right yellow button (4) cancels the ABA or AutoCarry cycle. The blade may be controlled manually at any time during the ABA or AutoCarry cycles.
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Located on the front of the dozer control lever is the trigger switch (not shown). When depressed and held, the trigger switch toggles between single tilt and dual tilt modes. Releasing the trigger switch toggles back to the default tilt mode. Either single tilt or dual tilt may be set as the default tilt mode using Cat Advisor. The left rocker switch (5) on the panel ahead of the dozer control lever, and below the Advisor panel is the ABA switch. It is used to arm the ABA mode. All of the Auto Blade Pitch settings for LOAD, CARRY, and SPREAD may be configured using Cat Advisor. The right rocker switch (6) manually activates the fan reversing cycle, if the machine is equipped with a reversing fan. NOTE: There are three different dozer control levers that can be installed in the D8T, depending on how the machine is equipped. The dozer control lever shown in illustration 6 is used on machines that are equipped with dual tilt. Machines equipped with dual tilt also include the ABA feature. If the machine is not equipped with dual tilt, but is equipped with AutoCarry, the control lever will look the same, but the thumb rocker switch is not active. If the machine has neither dual tilt nor AutoCarry (standard single tilt machine), the dozer control lever will not include the thumb rocker switch or the two yellow buttons.
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7 To the rear of the dozer control lever is the ripper control handle (1). Pulling back on the left side of the finger switch (2) moves the tip of the ripper SHANK IN. Pulling back on the right side of the finger switch moves the tip of the ripper SHANK OUT. At the left of the ripper control handle is the thumb switch (3), which controls RIPPER RAISE and RIPPER LOWER. Pushing against the top of the thumb switch RAISES the ripper. Pushing against the bottom of the thumb switch LOWERS the ripper. Pushing the Auto-Stow button (4) raises the ripper to the maximum height and can move the ripper tip to the full SHANK IN or full SHANK OUT position, depending on the operator settings configured using Cat Advisor. There are three Auto-Stow positions that may be configured: RIPPER RAISE, RIPPER RAISE/SHANK IN, or RIPPER RAISE/SHANK OUT. If the machine were equipped with a winch, the winch controls would be located in this same position. The winch control is similar to that used on the current D8R Series II Track-type Tractor, except that the drum clutch disconnect position has no detent.
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8 The panel on the outside of the right console contains a number of switches that control various machine functions. To the immediate right of the key switch is the High/Low Idle switch (1). Just above the High/Low Idle switch is the Implement Lockout switch (2), which disables implement movement and illuminates the Implement Lockout indicator light in the instrument cluster, when activated. Activating the Implement Lockout switch de-energizes the implement lockout solenoid, which shuts off the flow of pilot oil to the implement control valves. With no pilot oil available to the implement control valves, the implements cannot move. The AutoShift Mode switch (3) activates the AutoShift mode. The AutoShift mode may be configured using Cat Advisor, or by using Caterpillar ®Electronic Technician (Cat ET). The Auto KickDown Mode switch (4) enables the Auto KickDown mode, when activated. Shift-point sensitivity for the Auto KickDown mode (Low, Medium, and High) may be configured using Cat Advisor, or by using Cat ET. If the machine is equipped with AutoCarry, the AutoCarry Mode switch (5) arms the AutoCarry mode when activated.
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The ripper pin puller switch (6) is used to automatically retract and extend the ripper shank pin, if the machine is equipped with a single shank ripper. The four switches (7) at the rear of the console activate all the exterior machine lights.
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9 Located at the bottom front of the left console, and just inside the left cab door is the main fuse panel, circuit breakers, and diagnostic connector. Opening the hinged door gains access to: 1. the air conditioning remote condenser circuit breaker (if equipped - not shown, above) 2. the HVAC blower motor circuit breaker 3. the diagnostic connector for the Cat ET 4. the 12 volt switched power supply (for powering a laptop computer or other devices) 5. the 175 amp alternator fuse 6. the main electrical fuse panel, using automotive type fuses A fuse and breaker identification chart (7) is affixed to the inside of the hinged door. The chart shows fuse locations and identifies their associated electrical circuits. Several spare fuses, a spare 175 amp alternator fuse, and a fuse puller tool are also stored inside the hinged door. NOTE: The hinge on the door is spring loaded so that the door may be completely removed, if necessary.
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10 The HVAC controls and the wiper/washer controls are located overhead, above the right console. From left to right, these controls are: 1. HVAC blower fan speed switch, with four fan speed positions 2. HVAC temperature control 3. air-conditioning selector switch (ON/OFF) 4. front windshield wiper/washer control switch 5. left cab door wiper/washer control switch 6. right cab door wiper/washer control switch 7. rear cab window wiper/washer control switch
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11 The dash in the new cab contains an automotive style instrument cluster, which replaces the quad gauge module and the main display module with mode/alert indicators of the previous Caterpillar Monitoring System. The instrument cluster is a sealed unit that contains the following four analog gauges: 1. hydraulic oil temperature gauge 2. engine coolant temperature gauge 3. torque converter oil temperature gauge 4. fuel level gauge Also included in the instrument cluster is the tachometer (5) and up to fifteen indicator lights that alert the operator of different operational modes or conditions. The LCD display (6) below the tachometer displays the service hours at the bottom of the display, the track speed at the upper left, and the selected transmission gear and direction at the upper right. INSTRUCTOR NOTE: The instrument cluster and new monitoring system will be discussed in more detail, later in this presentation.
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12 Below the dash are the service brake pedal (1) and the decelerator pedal (2). The service brake pedal applies the service brakes (both left and right) proportionately with the amount of pressure applied by the operator. When depressed, the pedal provides a signal to the Power Train ECM from the rotary position sensor connected to the pedal. The Power Train ECM then signals the electronically controlled brake valve. When completely depressed, the brakes are fully engaged. The smaller pedal on the right is the decelerator pedal. During normal operation, the machine operates at high idle. Depressing the decelerator pedal decreases the engine rpm by a signal to the Engine ECM from the rotary position sensor connected to the pedal. Intermediate engine speeds are attained in the following manner. First, set the high/low idle switch to the HIGH IDLE position, and then depress the decelerator pedal to the desired engine speed. Then, press and hold the high idle (rabbit) side of the high/low idle switch for approximately three seconds and then release the switch to set the intermediate engine speed. The engine speed may then be reduced from this intermediate engine speed by depressing the decelerator pedal. When the decelerator pedal is released, the engine speed will return to the intermediate setting. The intermediate engine speed setting may be cancelled by pressing either the high idle (rabbit) or low idle (turtle) side of the switch again.
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13 The Power Train ECM (1) and the Implement ECM (2) are located at the rear of the cab. Accessing the Power Train ECM can be accomplished by removing the operator seat and the sound panel at the rear of the cab. The sound panel under the right console must also be removed to gain access to the Implement ECM. Other components located here are: 3. the J1/P1 connector for the Implement ECM 4. the J2/P2 connector for the Implement ECM 5. the J1/P1 connector for the Power Train ECM 6. the J2/P2 connector for the Power Train ECM 7. the exterior lighting relays NOTE: The Implement ECM and Power Train ECM code plugs are tied to the wiring harness, below the ECMs.
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14 CATERPILLAR MONITORING AND DISPLAY SYSTEM, WITH ADVISOR™ The monitoring system for the D8T has been upgraded to the Caterpillar Monitoring and Display System with Advisor. The major components in the new monitoring system consist of the Advisor graphical display module (1) and the in-dash instrument cluster (2). The graphical display module has a selfcontained ECM (Advisor ECM). Advisor allows the operator to configure machine and implement operation and the display options, then save them to an operator profile that may be selected whenever the operator desires. Advisor also allows the serviceman to configure certain password protected machine functions and to view system status information for the engine, the power train, the steering, and the implement systems. The serviceman can also perform calibrations of the machine and implement controls, the brakes and transmission, and the steering system through the Advisor panel.
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CATERPILLAR MONITORING AND DISPLAY SYSTEM COMPONENTS D8 T TRACK-TYPE TRACTOR + Implement ECM
J2
J1
Power Train ECM
Key St art Swit ch J2
J1
Engine ECM
J2
J1
(
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Navigat or / CTCT CAN A At t achment s Dat a Link Product Link
CAN A Dat a Link CAT Dat a Link 15
20
AUTO
25
10
5
AUTO
X1 0 0
n/ min
0
Dynamic Inclination Sensor
CAN B Dat a Link
Advisor
CAN C Dat a Link
30
35
2 .3
1F
1 3 2 .1
Inst rument Clust er
Comm Adapt er II
Fuel Level Sender Rear Act ion Lamp
Act ion Alarm
ET
Alt ernat or ( R-Terminal)
15 The Caterpillar Monitoring and Display System (CMDS) continuously monitors all machine systems. CMDS consists of both software and hardware components. The hardware components consist of the Cat Advisor graphical display module, a sealed instrument cluster, the Engine ECM, the Implement ECM, the Power Train ECM, the Action Alarm, the rear Action Lamp, and various switches, sensors, and senders. If the machine is so equipped, the CMDS may also include connections to a Product Link ECM, a Computer Aided Earthmoving System (CAES), and the Accugrade system and its components. The CMDS components communicate with each other and with electronic controls on the machine’s components through the Cat Data Link and through Controller Area Network (CAN) Data Links. A machine with standard equipment uses the Cat Data Link, the CAN A Data Link, and the CAN C Data Link. With AutoCarry attachments, CMDS will also include a CAN B Data Link (shown in dashed lines, above) and a CAN D Data Link (not shown, above). Advisor constantly monitors all of the ECMs, the alternator R-Terminal, the system input voltage, and the fuel level sensor, or sender. Advisor transmits the monitored data to the instrument cluster and activates its mode and alert indicators, displays, and gauges. This information may also be accessed and displayed on Advisor’s screens or with Cat ET.
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INSTRUMENT CLUSTER Auto KickDown Activated (5)
AutoCarry Charging Parking AutoShift Brake On (7) System Fault (9) Active (11) Activated (6) Action ABA Lamp (8) Enabled (10)
Float Active (13)
Winch Freespool or Release (4) Winch Low Speed Lock (3)
15
Single Tilt Enabled (14)
20
AUTO
25
10
AUTO
X100
Winch Disabled (2)
5
n/min
0
Engine Pre-Lube Activated (1)
Implement Lockout Activated (12)
30
35
2.3
Dual Tilt Enabled (15) Not Used
1F 132.1
Not Used
16 In addition to the four analog gauges, the tachometer, and the LCD display screen (mentioned earlier), the instrument cluster contains up to fifteen LED indicators that show the operator the status of a number of machine functions. When lit, they indicate the following functions: 1. Engine pre-lube activated (illuminates only if equipped with a pre-lube system) 2. winch disabled (illuminates only if the machine is equipped with a winch) 3. winch low speed lock (illuminates only if the machine is equipped with a winch) 4. winch freespool or release (illuminates only if the machine is equipped with a winch) 5. Auto KickDown activated 6. AutoShift activated 7. parking brake ON 8. Action Lamp 9. charging system fault (abnormal output at the "R" terminal) 10. Auto Blade Assist enabled (illuminates only if the machine is equipped with ABA) 11. AutoCarry active (illuminates only if the machine is equipped with AutoCarry) 12. implement lockout activated 13. FLOAT active 14. single tilt enabled 15. dual tilt enabled (illuminates only if the machine is equipped with dual tilt)
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17 The heart of the CMDS is the graphical display module, which is located on the right console, ahead of the dozer control lever. The graphical display module is referred to as Advisor. Advisor consists of the display screen (1), the navigational buttons (2), and an internal, self-contained ECM (not visible). Advisor is used to access, monitor, and display operating characteristics, diagnostics and events, and modes of operation. Advisor is also used to view and change operator preferences and parameters, much like the Vital Information Display System (VIDS) in the previous D10R Track-type Tractors. Advisor also allows the serviceman to troubleshoot and adjust machine systems by: - viewing active and logged codes and events, and clearing logged codes; - viewing the status of machine systems and their components; - and performing calibrations for the steering, the implement, and the power train systems.
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ADVISOR GRAPHICAL DISPLAY MODULE Gear/Direction Display Area
Dozer Mode Display Area
Auto-Shift Mode Display Area (1) Left / Up Arrow Button
1F
Float
(2) Right / Down Arrow Button
1F-2R
Home Menu Performance
(3) Back Button (Delete / Backspace Button)
Settings Operator Service
"More Options" Icon
OK
Data Display / Menu Selection Display Area
(4) Home Button
(5) OK Button (Enter / Select Button)
18 Cat Advisor is the interface between the operator or serviceman and the CMDS. Information is displayed on a backlit LCD screen. The top portion of the screen is called the "Top Banner" and it displays vital machine information at all times. The Top Banner may display different information from machine to machine, depending on the attachments and the machine configuration. On the base machine, the banner displays: - Transmission Gear and Direction, at the left; - Dozer Mode, in the center; - AutoShift Mode, at the right. The Transmission Gear and Direction display area shows the transmission gear and direction that is currently selected. The display may show any of the following transmission gear and direction combinations: "1F, 2F, 3F, 1R, 2R, 3R, or 1N."
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The Dozer Mode display area can display a number of messages which show the current dozer mode, the current segment during the Auto Blade Assist (ABA) cycle or AutoCarry cycle, or the status of the implement or the implement system. The Dozer Mode display area may show any of the following messages: - Carry (CARRY segment active - blade is in CARRY position) - Spread (blade is moving from CARRY to a preset SPREAD position) - Ready To Return (blade is at end of SPREAD segment - gear is Neutral) - Return (blade has reset - not in Forward gear) - Ready To Carry (blade is loading, next move will position for CARRY) - Manual (Manual blade mode active - ABA or AutoCarry not armed) - Not Reset (ECM does not know blade position) - Resetting (blade automatically moving to find load position) - Float (blade is in FLOAT - dozer control lever is in FLOAT position) - Low Engine Speed (engine speed too low for ABA/AutoCarry modes) - Wrong Gear (wrong gear for AutoCarry mode - shift the transmission to 1F) - Service (displayed during implement calibrations) - Implements Off (Implement Shutoff is ON, or active) - Stowing Ripper (ripper moving to stow position - AutoStow activated) The AutoShift Mode display area shows the current AutoShift Mode that is selected, using the AutoShift Mode selector switch on the right operator console. Depending on how the tractor is configured, it can display "1F-2R," "2F-2R," "2F-1R," or "Inactive," if no AutoShift Mode is selected. The bottom portion of the Advisor display screen is the Data Display/Menu Selection Display Area. It displays numerous menus and sub-menus used for navigation from screen to screen. It may also display operator warnings, system information, and system status, depending on what menu or sub-menu selection has been made. A "More Options" icon may also appear on the display screen. This is an indicator that more information is available for selecting or displaying from the current highlighted position. This icon may point down, up, left, or right. Using the Arrow Button that corresponds to the "More Options" icon will allow the operator or serviceman to move to and/or view the additional information. At the right of the display screen is a column of five User Interface buttons. These buttons are used to navigate through the numerous Advisor screens, to make menu selections, or to enter data.
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The five User Interface buttons, from top to bottom, are: 1. LEFT/UP Arrow button - This button is used for screen navigation or data entry. It can be used: - to scroll up a vertical list or scroll left across a horizontal list; - to decrease a setting value, such as decreasing brightness/contrast. 2. DOWN/RIGHT Arrow button - This button is also used for screen navigation or data entry. It can be used: - to scroll down a vertical list or scroll right across a horizontal list; - to increase a setting value, such as increasing brightness/contrast. 3. BACK button - This button is used: - to go up one level in a stair-step (hierarchical) menu structure, or to return to the previous screen, much the same as the BACK Button is used in Windows Internet Explorer™; - as a backspace, or cancel key when the operator or serviceman wishes to delete entered characters. 4. HOME button - This button is used to return to the home menu screen, regardless of what screen is currently displayed. 5. OK button - This button is used: - to make selections from a screen; - to confirm an entry, such as a password, or for saving an operator profile entry. Navigation through the menus and sub-menus is accomplished by using the ARROW buttons to highlight the desired selection, then pressing the OK button. The ARROW buttons are also used to highlight a mode or to set a parameter. Pressing the OK button selects that option. (Example: Choosing either "Enabled" or "Disabled" for the FLOAT option in the Implement Settings menu.)
NOTE: The column of five buttons at the left of the display screen currently have no function.
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1F
Text Reference
Float
1F-2R
Recall Operator Settings Default Settings
Display Setup in 10 Seconds Activated Or Press
OK
OK
To Recall Previous Settings
OK
19
Start Up Advisor will perform a self-test routine at machine start-up (key ON). After a few seconds, a preliminary screen will appear (illustration 19). The preliminary screen displays, "Default Settings Activated in 10 Seconds Or Press OK To Recall Previous Settings." To use the operator profile (settings) that were active the last time the machine was operated the operator may acknowledge "YES" by pressing the OK button. NO is assumed by waiting 10 seconds. If the operator answers YES by pressing the OK button, Advisor will load into its memory the operator profile that was last used. If the operator waits 10 seconds, the default settings (or factory settings) will be loaded into Advisor's memory. If the operator wishes to use an operator profile (settings) other than the last used set or the default settings, another operator profile may be selected from the "Operator" menu selection, from the Home Menu (see the "Operator Option" section, later in this module). After the preliminary screen has been acknowledged or has expired, "pop-up" warning screens may be displayed if there are any active faults in any of the machine systems (see illustration 20, next page).
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Float
1F Engine ECM MID 36
ID 164-3
Display Setup
Text Reference
1F-2R
!
OK
Injection Actuation Pressure Sensor Voltage Above Normal Shorted High
ACKNOWLEDGE PRESS THE OK KEY TO ACKNOWLEDGE
OK
20
The illustration above shows a "pop-up" warning screen generated by the Engine ECM and reported by Advisor. There may be more warning screens if there are any other active faults or events reported to Advisor by the Engine ECM, or any other ECM on the machine. Advisor will scroll through all of the warning screens generated by all of the active faults and events. Each of these warning screens must be individually acknowledged by pressing the "OK" button. Each of these warning screens contains the following information: - The reporting ECM (in text) - The reporting MID (module identifier, or ECM code) - The ID (Component ID and Failure Mode Identifier) - A text message stating the failed component - A text message stating the failure mode of the component - A prompt for the operator to acknowledge the warning Acknowledging these warnings does not clear them from the reporting ECM's memory. Acknowledging them only clears them from the screen, or "snoozes" them. They may re-occur after a pre-determined amount of time, depending on their severity. The CMDS provides three Warning Category Indicators (levels), utilizing "pop-up" warning messages on Advisor's screen (see above), the front Action Light (contained in the instrument cluster), the rear Action Lamp, and an Action Alarm.
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Text Reference
The three warning category indicators and the resulting combinations of the Action Lamps and the Action Alarm are: - Warning Category Indicator 1: A warning appears on the Advisor screen, describing the event or diagnostic failure. The forward Action Lamp will illuminate to solid amber. The warning can be acknowledged (snoozed) by pressing the OK button, and will not reappear for several hours, depending on the failure or event (or if the event or failure does not re-occur). - Warning Category Indicator 2: A warning appears on the Advisor screen, describing the event or diagnostic failure. The Action Light and Lamp will flash red, alerting the operator to change the machine operation mode. The warning can be acknowledged (snoozed) by pressing the OK button, and will not re-appear for one hour, depending on the event or failure (or if the event or failure does not re-occur) and the Action Light and Lamp will stop flashing. - Warning Category Indicator 3: A warning appears on the Advisor screen, describing the event or diagnostic failure. The Action Light and Lamp will flash red, and the Action Alarm will pulse to alert the operator to shut down the machine. The warning can be acknowledged (snoozed) and will continue to appear every five minutes. The Action Light and Lamp will continue to flash red and the Action Alarm will continue to pulse after the operator acknowledges the warning. NOTE: If the Warning Category Indicator (fault) is related to an implement control failure, the Advisor warning will ask if the operator desires to go to "Limp Home Mode." If the operator chooses the YES option, Advisor will display the Limp Home Screen. The Limp Home screen allows the operator to use Advisor to slowly and incrementally move the implements to a position that will allow the machine to be moved for service work. Gear selection for the transmission will be limited to first gear forward, or first gear reverse. NOTE: At machine start-up (key ON), the LCD display in the Instrument Cluster will briefly display the Instrument Cluster's part number. Although the T-Model tractors all have a common cab, the Instrument Cluster is different for the D8T, the D9T, and the D10T. This is due mainly because of differences in engine rpm between these models. The Advisor ECM software is model-specific also, reflecting the differences in Instrument Clusters. The Instrument Cluster and the Advisor software must match for the Instrument Cluster to operate properly.
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Text Reference
PERFORMANCE SCREEN 1 OF 2
Float
1F
1F-2R
Performance Engine Coolant Temp
1 of 2 Engine Speed
87.8 C Hydraulic Oil Temperature
n/min
21
1410 RPM TCO Temperature
76.6 C
68.8 C Next
OK
PERFORMANCE SCREEN 2 OF 2
Float
1F
1F-2R
Performance Engine Oil Pressure
2 of 2 Air Inlet Temperature
506.0 kPa Fuel Level
75 % Previous
22
40 C System Voltage
26.3 Volts OK
After the warning screens have been acknowledged the "Performance 1 of 2" screen will then appear on the display (illustration 21). This is the default screen. Pressing the right ARROW button will display the "Performance 2 of 2" screen (illustration 22). Using the left and right ARROW buttons allows the operator to switch back and forth between the two Performance screens. Vital information about the machine's major systems may be easily monitored using these two screens and the in-dash Instrument Cluster.
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Text Reference
The two Performance screens display real-time text information for the following: - Engine Coolant Temperature - Engine Speed - Hydraulic Oil Temperature - Torque Converter Oil Temperature - Engine Oil Pressure - Air Inlet Temperature - Fuel Level - System Voltage The Home Menu may displayed from any screen by pressing the HOME button. INSTRUCTOR NOTE: For more detailed information about the new monitoring system and Advisor and how to access and use all of the options, refer to SERV1790, "Caterpillar Monitoring and Display System with Advisor™ for Track-type Tractors."
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Text Reference
23 ENGINE The C15 ACERT™ technology engine is new for the D8T Track-type Tractor. The engine is equipped with Mechanical Electronic Unit Injection (MEUI), an Air To Air AfterCooler (ATAAC), and a new electro-hydraulic demand fan system. The C15 engine also utilizes the A4 Engine Electronic Control Module (ECM), which is air cooled. The C15 is rated at 231.6 net kW (310 net horsepower) at 1850 rpm. The D8T uses a "constant net" power strategy. This means that at rated speed, and under full load, the tractor always delivers 231 kW (310 hp) at the flywheel, except during derates. When the demand fan is at maximum speed, the Engine ECM increases gross power to 259 kW (347 hp). At minimum fan speed, the Engine ECM maintains gross power at 243 kW (326 hp). This strategy maintains a constant net power regardless of fan requirements and provides fuel consumption benefits during low ambient conditions. The C15 engine is an in-line six-cylinder arrangement, with a displacement of 15.2 liters. Most of the service points for the C15 are located on the left side of the engine. The C15 engine meets U.S. Environmental Protection Agency (EPA) Tier III Emissions Regulations for North America and Stage III European Emissions Regulations.
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Text Reference
Engine oil and filter change intervals have been increased to 500 hours, under most operating conditions. However, engine load factor, sulfur levels in the fuel, oil quality, and altitude may negatively affect the extended oil change intervals. Regular engine oil samplings (S•O•S) must be performed every 250 hours to confirm oil cleanliness. The C15 is functionally similar to the 3406E engine used in the D8R Series II. However, the Engine ECM and its software, the cam, the injectors, the crankshaft, the piston rods, the pistons, and a few other components are re-engineered, reflecting the change to ACERT technology. An electro-hydraulic demand fan is standard equipment for the D8T. The D8T may also be equipped with an automatic/manual fan reversing feature for some applications. The C15 ACERT technology engine specifications for the D8T Track-type Tractor are: -Serial No. Prefix: LHX -Performance Spec: 0K4648 (for North America), and 0K4147 (for E.U.) -Max Altitude: 3810 m (12,500 ft.) without derate -Gross Power: 259 kW (347 hp) -Net Power: 231 kW (310 hp) -Full Load rpm: 1850 -High Idle rpm (full throttle, neutral): 2200 ± 10 (for North America), 2070 ± 10 (for E.U.) -Low Idle rpm: 700 NOTE: The C15 engine uses a "Ground Speed Governor" engine software strategy to reduce the potential for engine overspeed and to maintain a constant speed in downhill and uphill situations when there is little or no load on the blade. The Engine ECM constantly monitors engine speed and torque converter output speed to make the following adjustments. - If the engine is at high idle while the machine is traveling downhill, the Engine ECM will automatically lower engine rpm to maintain the correct torque converter output speed. In uphill situations, the Engine ECM will automatically increase engine rpm to maintain the correct torque converter output speed, up to a maximum of 2200 rpm. - If the engine is in an overspeed condition (2600+ engine rpms), the Power Train ECM will automatically apply the brakes (up to 8% of brake capacity) in an effort to slow the machine. If this auto-braking strategy does not lower engine rpms to an acceptable level, Advisor will warn the operator to change the operating mode (downshift or manually apply the brakes). - If the operator has set an intermediate engine speed using the decelerator and the highlow idle switch, this strategy is ignored in uphill situations. On machines built for the E.U., the torque converter output speed target is approximately 5% lower than those built for North America, due to more stringent noise requirements. Accordingly, the ground speed target is a bit slower, also. This will result in slightly slower speeds when "roading" the machine and when backing up.
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2
3
4
Text Reference
5
6 7
1
8
11
9
10
24 Major service points accessible from the left side of the engine are: 1. coolant sampling port (S•O•S) 2. engine oil fill tube 3. engine oil filter and associated service points (discussed later in this presentation) 4. air filter access cover 5. engine oil dipstick 6. primary fuel filter and water separator and electric fuel priming pump 7. secondary fuel filter and associated sensors (discussed later in this presentation) 8. A4 Engine ECM 9. starter 10. prelube motor and pump (if equipped) 11. high-speed oil change connectors for engine oil and power train oil
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1
Text Reference
2
8 3
4
5 7
6
25 Major service points accessible from the right side of the engine are: 1. turbocharger 2. air conditioning compressor 3. thermostat (temperature regulator) housing 4. alternator 5. coolant flow switch 6. external engine oil cooler 7. power train oil cooler 8. block heater element
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5
Text Reference
4
6
3
7
8
1
9
2
26 Located on the left side and toward the rear of the engine is the 10-micron primary fuel filter (1). The primary fuel filter contains a water separator which removes water from the fuel. Water in a high pressure fuel system can cause premature failure of the fuel injectors due to lack of lubricity and corrosion. Fuel is drawn from the primary fuel filter by the fuel pump (shown later) and is then returned to the 2-micron secondary fuel filter (2). The secondary fuel filter removes all contaminants that could damage the fuel injectors. Fuel filters should be replaced regularly, according to the guidelines on the D8T Operation and Maintenance Manual (SEBU7763) to ensure that clean fuel is always delivered to the fuel injectors. The electric fuel priming pump (4) is integrated into the primary fuel filter base. It is activated by pushing the electric fuel priming pump switch (5). Also shown is the fuel system air purge valve (3), which is used to purge the priming pump of any air that might be introduced after changing the fuel filters. The fuel priming pump is used to fill the fuel filter housings after the filter elements have been replaced. The fuel priming pump is capable of forcing the air from the entire fuel system. After the fuel filters have been replaced, activate the priming pump and then open the air purge valve. (Always place a suitable container under the purge valve outlet to catch any fuel that escapes through the valve.)
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Text Reference
Trapped air and a small amount of fuel will escape through the purge valve as the pump primes itself. When the purge valve emits only fuel, the purge valve should then be closed. Continue operating the priming pump until it is determined that all air has been forced from the entire fuel system - from the priming pump to the fuel tank. It should be noted that the priming pump produces enough pressure to force fuel past the bypass valve in the fuel transfer pump and past the fuel pressure regulator (check valve). Also note that the main disconnect switch must be turned to the ON position and the key start switch must be in the OFF position for the fuel priming pump to run. Also visible in the illustration above is the block heater receptacle (6). 120V and 240V versions of the block heater are available. Also shown is the auxiliary start receptacle (7), which may be used to supplement the batteries when the temperatures are extremely cold or the batteries are low. The ether aid solenoid (8) is also shown in illustration 26 (the ether canister is not installed). When the ether aid solenoid is energized, ether is injected into the intake manifold inlet tube (9). The Engine ECM controls ether injection when the conditions warrant its use. The Engine ECM monitors the intake air temperature sensor and the coolant temperature sensor to determine when to inject ether. If the temperature of the engine coolant or the intake air is less than 0°C (32°F), AND the engine speed is greater than 35 rpm, but less than low idle speed (700 rpm), then ether injection will be activated. Once the engine starts and the low idle speed is attained, the Engine ECM then looks to the ether injection map (contained in the engine software) to determine how long to provide ether injection. The status of the ether aid solenoid may be viewed through the Advisor Panel (Engine System Status screens) or by using Cat ET.
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4
Text Reference
3
2
1
27 Installed in the top of the secondary fuel filter base are the following fuel system components: 1. fuel temperature sender 2. fuel pressure regulator (check valve) 3. fuel pressure sensor 4. secondary fuel filter bypass switch (differential pressure switch) The status of the fuel temperature, the fuel pressure, and the state of the secondary fuel filter bypass switch may be viewed through the Advisor panel (Engine System Status screens) or through Cat ET.
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2
Text Reference
3
1
5
4
28 The fuel transfer pump (1) is located at the front left of the engine, near the bottom of the engine. The fuel transfer pump is driven by the front gear train. Fuel is drawn from the primary fuel filter and water separator through the upper fuel line (2) by the fuel transfer pump and is returned to the secondary fuel filter through the lower fuel line (3). The primary (crankshaft) engine speed/timing sensor (4) is located just below the fuel transfer pump. The crankshaft speed/timing sensor provides crankshaft speed and position information to the Engine ECM. This information is also shared with the Power Train ECM as engine speed information. The C15 engine has no engine output speed sensor at the flywheel housing. This is a change from the D8R Series II, which had an engine output speed sensor installed in the flywheel housing which provided engine speed information to the Power Train ECM. The timing calibration probe adapter (7X1171) is threaded into the timing calibration port (5), after removing the plug. The timing calibration probe, or transducer (6V2197), is then inserted into the adapter. Maintain a 1 mm (.040") air gap between the end of the probe and the machined surface of the crankshaft counterweight when positioning the probe. The probe will sense a notch that is machined in the crank counter-weight. Cable 7X1695 is used to connect the probe to the timing calibration connector (illustration 31).
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Text Reference
1
2
4
3
29 The engine pre-lube pump (1) is driven by an electric motor (2). (The pre-lube pump is no longer driven by the starter motor.) If the machine is equipped with pre-lube, the pre-lube pump and motor are installed on the left side of the engine, just above the oil pan. Engine pre-lube is used to ensure that there is sufficient oil pressure throughout the engine oil system before allowing the starter to engage and start the engine. This strategy prevents premature wear of critical engine components. When the key start switch is moved to the START position, the prelube pump may run for a short time before the starter engages. The Engine ECM determines when to activate the pre-lube pump by monitoring the engine oil pressure sensor. If the oil pressure is less than 30 kPa (4.4 psi) the Engine ECM will activate the pre-lube pump until the oil pressure reaches 30 kPa (4.4 psi), or for up to 45 seconds, whichever occurs first. To override this strategy, turn the key switch to the START position. Then cycle the key start switch to the OFF position and then back to the START position again within one second. This action will allow the starter to engage without cycling the pre-lube pump. The ecology drain (3) for engine oil is located on the left side of the oil pan. The steel tube (4) to the rear of the pre-lube pump connects to the Quick-Evac connector for engine oil. NOTE: When the pre-lube cycle is activated, Advisor will inform the operator that prelube is activated and to keep the key start switch in the "START" position until the engine is running.
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Text Reference
2 1
30 The atmospheric pressure sensor (1) and the engine oil pressure sensor (2) are installed in a block that is located on the lower left side of the engine, between the pre-lube pump and the starter. The status of these two pressure sensors may be viewed through the Advisor panel (Engine System Status screens) or through Cat ET. Engine oil pressure may also be viewed on the Performance Screen 2 of the Advisor display.
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Text Reference
5
4
6
3
2
1
31 The starter (1) is located on the left side of the engine, and is mounted to the front side of the flywheel housing. Just above the starter is the air cooled A4 Engine ECM (2). The timing probe connector (3) is fastened to the wiring harness coming from the J2/P2 connector (4). The J1/P1 connector (5) is a 70-pin connector and the J2/P2 connector is a 120-pin connector. The hydraulic hose and fitting (6) supplies lube oil to the flywheel housing. The other end of the hose is connected to a fitting on the side of the torque converter oil inlet port, at the left rear of the torque converter housing. A small amount of power train oil flows through the hose to provide lubrication for the flywheel and pump drive gears. The power train scavenge pump returns the oil from the bottom of the flywheel housing to the power train main sump.
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Text Reference
2
1
32 Also accessible from the left side of the engine, and located just above the starter, is the cover for inserting the engine turning tool (1). Removing this cover allows the serviceman to insert the 9S9082 engine turning tool to manually turn the engine. To find Top Dead Center (TDC) of cylinder number one, remove the plug in the TDC port (2), then insert the longer bolt from the cover (1) into the port (2). While applying light pressure to the bolt, turn the engine in the direction of engine rotation until the bolt drops into the hole machined in the front face of the flywheel. A spring-loaded timing pin (136-4632) may also be used to find TDC, instead of the long bolt from the cover.
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Text Reference
1
33
4
3
2
34
The intake air temperature sensor (1) is located on the left side of the engine, just below the primary fuel filter and water separator. The status of this pressure sensor may also be viewed through the Advisor panel (Engine System Status or Performance screen) or through Cat ET. The "Crank-Without-Inject" connector (2) is fastened to the wiring harness just below and in front of the intake manifold. Removing the plug (3) from the "Crank-Without-Inject" connector (2) and inserting the plug (4) at the left will electronically disable the fuel injectors. This allows the engine to be turned (cranked) using the starter, but without the engine starting. No fuel will be injected into the cylinders in this mode so that the engine cannot start and run. The status of the "Crank-Without-Inject" feature may be viewed through the Advisor panel (Engine System Status screens) or through Cat ET.
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Text Reference
3 4
5
2
1
35 Located at the left front of the engine, are the following service points: 1. engine oil filter 2. engine oil filler tube 3. engine oil sampling port (S•O•S port) 4. engine oil pressure port 5. engine oil dipstick NOTE: The engine oil pressure port tests the engine oil pressure after the oil is filtered. The engine oil sampling port is positioned upstream of the oil filter so an oil sample reflects the cleanliness of the oil before the filter.
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Text Reference
1 36
37
2
The intake manifold air (boost) pressure sensor (1) is located at the upper left, and at the front of the engine, just ahead of the engine oil filter. Also located here, and installed in the rear of the timing gear cover, is the secondary (camshaft) engine speed/timing sensor (2). The status of the intake manifold pressure sensor may be viewed through the Advisor panel (Engine System Status screens) or through Cat ET.
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Text Reference
2
38
1
3 2
4 39
5
6
The coolant temperature sensor (1) is installed at the right front corner of the engine, in front of the water pump (2). The status of the coolant temperature sensor may be viewed through the Advisor panel (Engine System Status screens or Performance screen) or through Cat ET. The water pump (2) is located behind and below the alternator, at the right front of the engine. Just above the water pump is the thermostat (coolant temperature regulator) housing (3). Two thermostats are contained in the housing. The shutoff valve for the cab heater return line (4) and the shutoff valve for the cab heater supply line (5) are located to the rear of the thermostat housing. The coolant flow switch (6) is situated outboard from the thermostat housing and installed in the cast tube exiting the water pump. The status of the coolant flow switch may be viewed through the Advisor panel (Engine System Status screens) or through Cat ET.
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Text Reference
3
2
1
40
6
41
5 4
Also accessible at the right front of the engine is the alternator (1) and the air-conditioning compressor (2). Just to the rear of the air-conditioning compressor is the turbocharger (3). The turbocharger on the C15 ACERT technology engine uses a standard wastegate (4), which is operated by a vacuum line (5). The wastegate acts as a bypass valve for exhaust gasses. When the wastegate opens it allows some of the exhaust gasses to bypass the turbocharger. The wastegate limits boost pressure, which in turn, limits the maximum engine cylinder pressure. The center section of the turbocharger is water cooled (line not visible) and is lubricated with engine oil, which is supplied through the hard steel tube (6).
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6
5
Text Reference
4
3 2
1
42 The oil-to-water type engine oil cooler (1) is located along the lower right side of the engine. Oil from the oil filter enters the cooler at the oil inlet (2) and passes through tubes surrounded by engine coolant. The cooled oil then exits the cooler at the oil outlet (4) and enters the engine block at port (5). When the engine is started and the oil is cold, some of the oil bypasses the engine oil cooler through the cooler bypass tube (3). Coolant enters the engine oil cooler at the front (right, above) of the cooler and exits at the rear, where it then enters the power train oil cooler (6). After flowing around the oil filled tubes in the power train oil cooler, the coolant enters the right side of the engine block through a port (not visible) behind the power train oil cooler. NOTE: When troubleshooting the cooling system it must be understood that both the engine oil cooler and the power train oil cooler are heat sources that raise the temperature of the coolant before it enters the engine block.
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Text Reference
1
2
43
The turbo inlet pressure sensor (1) is installed at the outlet of the air filter canister and is accessible from the right side of the engine. The turbo inlet air pressure sensor is used to determine air filter restriction. The Engine ECM compares the turbo inlet air pressure to the atmospheric air pressure and calculates a pressure differential between the two pressures. If the pressure differential is too great, it can indicate that the air filter is clogged and needs to be replaced. Also visible in this illustration is the dust ejector tube (2) that connects the intake air precleaner to the muffler. The status of the turbo inlet air pressure sensor may be viewed through the Advisor panel (Engine System Status screens) or through Cat ET.
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Text Reference
C15 ACERT ENGINE FUEL DELIVERY SYSTEM D8T TRACK-TYPE TRACTOR
Fuel Tank
Fuel Pressure Regulator
Fuel Gallery Electric Fuel Priming Pump
Fuel Transfer Pump
Primary Fuel Filter
Secondary Fuel Filter
44 Fuel System Fuel is drawn from the fuel tank through the primary fuel filter (10-micron) and water separator by a gear-type fuel transfer pump. The fuel transfer pump then directs the fuel through the secondary fuel filter (2-micron). From the secondary fuel filter,the fuel is then directed to the cylinder head and into the fuel gallery, where it is made available to each of the six MEUI fuel injectors. Any excess fuel not injected leaves the cylinder head. From the cylinder head, the fuel is directed back to the fuel tank through the fuel pressure regulator, which maintains fuel pressure of 558 ± 50 kPa (81 ± 7 psi). The fuel pressure regulator is a check valve that is installed in the secondary fuel filter base. From the fuel pressure regulator, the excess fuel flow returns to the fuel tank. The ratio of fuel between combustion and fuel returned to tank is approximately 3:1 (i.e. four times the volume required for combustion is supplied to the system for combustion and injector cooling purposes). A differential pressure switch is installed in the secondary fuel filter base and will alert the operator, via Advisor, of a clogged fuel filter. This Advisor warning indicates that the secondary fuel filter is being bypassed and that the fuel filter should be replaced immediately. The recommended fuel filter change frequency interval is 500 hours, under optimum conditions.
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Text Reference
1
2
4
3
7 6
5
45 Engine Air System Air is drawn into the engine air pre-cleaner (1) by the vacuum created by the compressor wheel in the turbocharger (3). Exhaust gasses passing through the muffler flow past the dust ejector tube, which is connected to the pre-cleaner by a hose (2). This creates a secondary vacuum in the pre-cleaner housing which draws large contaminant particles from the pre-cleaner through the tube. The large particles are then ejected through the muffler and exhaust stack. The intake air is then drawn through the air cleaner (4) where the fine contaminants are removed by the filter element. The clean intake air is then drawn into the air inlet of the turbocharger. The turbocharger compresses the air and pushes it out of the compressor outlet. The compressed air then enters the Air To Air AfterCooler (ATAAC) inlet (5). As the intake air passes through the ATAAC core, it is cooled and then exits the ATAAC through the ATAAC outlet (6). The compressed, cooled intake air is then directed to the intake manifold where it enters the cylinder head. The cooler, more dense air results in greater combustion efficiency and fewer emissions. Boost pressure may be read on the status screen in Cat ET. The boost pressure is a calculation of the difference between the atmospheric pressure and the intake manifold air pressure. A failure of the intake manifold air pressure sensor can cause the Engine ECM to perceive a "zero boost" condition, resulting in a reduction in power (derate) by as much as 60%.
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Text Reference
D8T COOLING SYSTEM Fill Tube and Cap Shunt Tank
> 92°C
87°C
< 81°C
Hottest
Increasing Coolant Temperature Coldest
Thermostat Housing
Turbo
Power Train Oil Cooler
Bypass Tube
Jacket Water Pump Engine Oil Cooler
Vent Line
ATAAC (Far Side)
Hydraulic Oil Cooler
Cab Heater
C15 Engine
AMOCS Radiator
Hydraulic Demand Fan
46 Cooling System Shown above is a schematic of the cooling system for the D8T Track-type Tractor with the C15 ACERT technology engine. The C15 uses an Air To Air AfterCooler (ATAAC) to cool the intake air. The ATAAC is mounted vertically in the radiator guard (not pictured, in the above illustration). It is in line with, and to the left of the AMOCS radiator cores. The hydraulic oil cooler is an oil-to-air type cooler and is mounted vertically, behind the AMOCS cores. The AMOCS radiator contains six cores and are the standard "two-pass" design. The hydraulic demand fan is controlled by the Engine ECM. The fan mounted on the front of the radiator guard and is situated in front of the radiator. This arrangement draws air in through the sides of the engine compartment, then through the hydraulic oil cooler, the radiator and the ATAAC, then exits the front of the tractor. This design minimizes the possibility of the fan ejecting debris into the radiator or ATAAC cores (when the fan reversing feature is not activated). Coolant flows from the water pump, through the engine oil cooler, then through the power train oil cooler, and then into the engine block. Coolant then flows through the engine block and into the cylinder head.
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Text Reference
From the cylinder head, the coolant flows to the temperature regulators (thermostats) and either goes directly to the water pump through the bypass tubes or to the radiator, depending on the temperature of the coolant. When the engine is cold, the coolant flows directly to the water pump through the bypass tube. As the temperature of the coolant increases, the thermostats open and the coolant then flows to the radiator. The thermostat housing for the C15 engine contains dual thermostats. The opening temperature for these thermostats is 81° - 84°C (178° 183°F). The thermostats should be fully open at 92°C (198°F). Hot coolant enters the bottom of the radiator and it is cooled the first time as it flows upward through the front side of the AMOCS cores. The coolant is cooled a second time as it flows down the back side of the cores. The coolant then exits the radiator and returns to the water pump. A small amount of coolant flows to the turbocharger from the thermostat housing, for cooling purposes, and is then directed to the shunt tank. Coolant from the shunt tank is directed to the water pump. The fill tube and the radiator cap for the cooling system are located on top of the shunt tank. The shunt tank is located directly above the radiator core in the engine compartment. Access to the fill tube is provided by lifting a spring hinged door on top of the radiator guard. A sight glass in the shunt tank is visible from the left side of the engine compartment. The sight glass should always be filled with coolant. If any air is seen in the sight glass, coolant needs to be added to the system through the cap on the shunt tank. The air vent lines remove air from the cooling system while the system is being filled and during operation. The shunt tank is a reservoir and retains the expansion volume of the coolant as the coolant temperature increases. The level of the coolant in the shunt tank will rise as the coolant increases in temperature. The coolant level in the shunt tank will fall as the temperature of the coolant decreases. A drain valve (illustration 48) is present below the radiator and is used to drain coolant from the radiator cores, the engine oil and power train oil coolers, and the cab heater circuit.
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Text Reference
3
5 47
2
1
4
7
6
9
48
8
Mounted vertically on the back side of the D8T radiator guard is the hydraulic oil cooler (1). In front of the hydraulic oil cooler are the six AMOCS radiator cores (2). At the top of the radiator guard is the shunt tank (3). Mounted vertically on the left side of the radiator guard is the air conditioning condenser (4). In front of the condenser, and to the left of the AMOCS cores is the ATAAC core (5). Hot coolant enters the radiator at the inlet tube (6). It flows up through the front side of the AMOCS cores, then down the back side, passing twice through the cores. The coolant then exits the radiator through the outlet tube (7) and returns to the water pump. The radiator drain line from the oil coolers (8) and the drain valve (9) can also be seen here.
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Text Reference
1
2
3
49
Opening the grill on the front of the radiator guard gains access to the fan (1) (behind the brush guard) and the hydraulic demand fan motor (2) with a self-contained anti-cavitation valve. If the machine is equipped with a reversing fan, a bi-directional fan motor replaces the standard fan motor with anti-cavitation valve. The fan reversing valve (3) is located at the lower left of the radiator guard. INSTRUCTOR NOTE: The hydraulic demand fan and the reversing fan strategy will be discussed later in this presentation.
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Text Reference
D8T STANDARD HYDRAULIC FAN DRIVE SYSTEM MAXIMUM FAN SPEED
Engine Coolant Temperature Sensor Intake Air Temperature Sensor
Hydraulic Oil Temperature Sensor
Implement ECM
Fan Motor
Pump Control Valve
Pilot Drain from Dual Tilt Valve
Engine ECM Fan Pump Pressure Control Solenoid
Pump Pressure Sensor HFPD
Cooler Bypass Valve
Drive from Steering Pump
Demand Fan Pump
Hydraulic Oil Cooler
To Case Drain Manifold From Suction Manifold
To Suction Manifold
50 Hydraulic Demand Fan System Standard on the D8T Track-type Tractor is the hydraulic demand fan. Although the fan is part of the hydraulic system, it is controlled by the Engine ECM. The Engine ECM considers four inputs for controlling the fan. The hydraulic oil temperature sensor, the engine intake air temperature sensor, and the engine coolant temperature sensor all provide temperature information to the Engine ECM. The Engine ECM monitors all three of these temperature inputs. The highest temperature (relative to the percentage of its temperature map) is the controlling temperature for fan speed. The fan pump discharge pressure sensor is the fourth input to the Engine ECM. Fan pump discharge pressure is controlled by the Engine ECM to determine fan speed. The Engine ECM monitors the temperature inputs and also considers fan pump discharge pressure to provide a signal to the (proportional) fan pump pressure control solenoid. When the solenoid receives minimum current from the Engine ECM, maximum flow is sent to the fan motor, causing the fan to turn at the maximum controlled rpm (about 1350 + 25 rpm), as shown above. Maximum mechanical pump pressure (high pressure cutoff - no current or a failed solenoid) is set to approximately 15000 + 860 kPa (2175 + 125 psi). Maximum pressure regulated by the Engine ECM software is approximately 13250 + 500 kPa (1922 + 75 psi).
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Text Reference
Cat ET may be used to reset the maximum controlled fan system pressure from the maximum pressure set at the factory. This adjustment may be necessary to correct the maximum controlled fan speed due to differences in altitude between the factory and the tractor's work site. In cooler weather, the Engine ECM may utilize an engine software strategy called "Cool Engine Elevated Idle Strategy" when the following conditions are met: - Coolant Temperature < 70°C (158°F) - Parking brake is set to ON - Transmission in NEUTRAL - Throttle switch set to LOW IDLE Under these conditions, the Engine ECM will automatically increase engine speed, up to 1100 rpm, in an effort to increase coolant temperature. When any of the four conditions are not met, the strategy is ignored. NOTE: The D8T does not utilize a fan bypass valve for cold weather.
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Text Reference
D8T STANDARD HYDRAULIC FAN DRIVE SYSTEM MINIMUM FAN SPEED
Engine Coolant Temperature Sensor Intake Air Temperature Sensor
Hydraulic Oil Temperature Sensor
Implement ECM
Fan Motor
Pump Control Valve
Pilot Drain from Dual Tilt Valve
Engine ECM Fan Pump Pressure Control Solenoid
Pump Pressure Sensor HFPD
Cooler Bypass Valve
Drive from Steering Pump Demand Fan Pump
Hydraulic Oil Cooler
To Case Drain Manifold From Suction Manifold
To Suction Manifold
51 The standard hydraulic demand fan schematic with the fan at minimum speed is shown above. If maximum fan speed is not required, the fan pump pressure control solenoid is energized, causing the fan to turn at a slower speed. Minimum fan speed is attained when the fan pump pressure control solenoid is completely energized (approximately 450 + 50 rpm). Fan pump pressure at minimum speed should be set to approximately 1827 ± 240 kPa (265 ± 35 psi). If communication is lost between the Engine ECM and the fan pump pressure control solenoid, the fan will default to the maximum mechanical pressure setting, which is approximately 15000 + 860 kPa (2175 + 125 psi). This results in a fan speed of approximately1369 rpm (as set at the factory). NOTE: If the engine is in the overspeed condition, the Engine ECM will regulate the fan toward minimum pressure in an effort to protect the fan hydraulic system.
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Text Reference
D8T FAN PUMP AND CONTROL VALVE MAXIMUM CONTROLLED FAN SPEED
Piston and Barrel Assembly
Fan Pump
Adjustment Screw
Pressure Control Solenoid
Case Drain Passage
Pump Output to Fan Motor
Spring Pin Pressure Control Spool
Orifice
Spring
Pump Control Spool
Bias Spring Swashplate Actuator Piston
Adjustment Screw
52 As stated earlier, the Engine ECM constantly monitors the intake air temperature, the engine coolant temperature, and the hydraulic oil temperature. When temperatures require maximum controlled fan speed, the Engine ECM de-energizes the fan pump pressure control solenoid, sending the least amount of signal, as shown above. (When communication is lost to the pump control solenoid and no current is sent to the solenoid, the mechanical high pressure cutoff will raise the fan speed to its absolute maximum speed.) With the solenoid de-energized, the pressure control spool spring forces the top half of the pressure control spool up. This blocks pump output oil in the pump control spool spring chamber from draining to tank through the case drain passage, which causes the pump control spool spring chamber to become pressurized. The force of the spring at the top of the pump control spool, plus the pressure of the oil, is then greater than the oil pressure at the bottom of the pump control spool. The pump control spool is held down, blocking pump output oil from entering the signal passage to the actuator piston in the pump. The actuator piston is then open to drain. With only tank pressure in the actuator piston, the bias spring moves the pump swashplate to an increased angle, causing the pump to UPSTROKE, providing controlled maximum flow to the fan motor. This condition results in maximum controlled fan speed.
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Text Reference
D8T FAN PUMP AND CONTROL VALVE MINIMUM FAN SPEED
Piston and Barrel Assembly
Fan Pump
Adjustment Screw
Pressure Control Solenoid
Case Drain Passage
Pump Output to Fan Motor
Spring
Pin Pressure Control Spool
Orifice
Spring
Pump Control Spool
Bias Spring Swashplate Actuator Piston
Adjustment Screw
53 When a slower fan speed is required, the Engine ECM energizes the fan pump pressure control solenoid (proportional to temperature data) as shown above. With the solenoid energized, the solenoid pin pushes down on the top half of the pressure control spool, against the force of the pressure control spool spring. This allows oil in the pump control spool spring chamber to drain to tank through the case drain passage, lowering the pressure in the spring chamber. The force of the spring at the top of the pump control spool plus the pressure of the oil is now less than the oil pressure at the bottom of the pump control spool, due to the orifice effect of the passage through the pump control spool. The pump control spool then moves up, allowing pump output oil to enter the signal passage. This flow of oil to the pump actuator piston causes pressure in the pump's actuator piston to increase. The increased pressure in the actuator piston overcomes the force of the pump bias spring. This causes the swashplate to move to a decreased angle, and the pump DESTROKES. The pump then provides less flow to the fan motor, resulting in a slower fan speed. The illustration above shows the fan pump at minimum angle, or minimum flow. This will cause the fan motor to turn at its slowest speed. Refer to RENR7527, "Systems Operation/Testing and Adjusting for the D8T Track-type Tractor Hydraulic System" for information regarding adjustment of the hydraulic demand fan.
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Text Reference
D8 T HYDRAULIC FAN DRIVE SYSTEM WITH REVERSING VALVE
Pump Cont rol Valve
MAXIMUM FAN SPEED - REVERSE
Fan Reversing Valve
Fan Pump Pressure Cont rol Solenoid Pilot Drain from Dual Tilt Valve
Bi-Direct ional Fan Mot or
HFPD Crossover Relief Valves
Int ake Air Temp. Sensor
Implement ECM
Demand Fan Pump
Hydraulic Oil Cooler
Coolant Temp. Sensor
Fan Reversing Valve Cont rol Solenoid
To Case Drain Manifold
Hydraulic Oil Cooler Bypass Valve
Hydraulic Oil Temp. Sensor
Fan Pump Pressure Sensor
Suct ion Manifold From Cold Oil Relief Valve To Implement Pump
Engine ECM
To St eering Charge Pump
54 If the machine is equipped with a reversing fan, a fan reversing valve will be installed at the lower left front of the radiator guard and a bi-directional fan motor will replace the standard fan motor. For machines equipped with the optional reversing valve, the Engine ECM will automatically activate the fan reversing valve solenoid at pre-determined intervals (engaged in reverse gear only). Fan reversing intervals and duration are programmable using Cat ET. The fan may also be reversed manually using the manual reversing fan switch, which is located ahead of the dozer control lever, and just below the Advisor display screen. The illustration above shows the fan hydraulic system with the reversing function activated. Activating the manual reversing fan switch energizes the reversing solenoid valve. This action directs some of the oil to shift the two pilot operated reversing valves, which in turn reverses the flow of oil to and from the fan motor. The fan will then reverse directions, causing air to flow in the opposite direction through all the cooler cores (radiator, ATAAC, and hydraulic oil cooler). When the engine software determines it is time for the fan to reverse directions, it will energize the reversing valve solenoid only when the transmission is shifted to reverse. This strategy helps minimize the chances that any material spilling over the top of the dozer blade (when pushing material) will be ejected into the fan blades and secondarily, into the radiator cores. This strategy helps minimize the potential for damage to the fan blades and the radiator fins.
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Text Reference
1 2
55
3 6
4 5
7
8
56
9 10
The hydraulic demand fan pump (1), is mounted to the rear of the steering pump, at the upper left of of the flywheel housing. Shown is the pressure tap for Hydraulic Fan Pump Discharge pressure (HFPD) (2), the fan pump pressure sensor (3), the fan pump pressure control solenoid (4), the pump control spool adjustment screw (5), and the pump pressure control spool (6). The hydraulic demand fan motor is mounted to a bracket at the front of the radiator guard. Visible in illustration 56 is the fan motor (7), the fan motor case drain line (8), and the fan motor inlet and outlet ports (9). The fan reversing valve (10) is only present on machines equipped with the reversing fan attachment. The status of the fan pump pressure sensor may be viewed through the Advisor panel (Engine System Status screens) or through Cat ET.
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Text Reference
4
5 3
1 2
57
For machines equipped with a reversing fan, the fan reversing valve (1) is mounted in the lower left corner of the radiator guard, just behind the grill doors. Service points on the fan reversing valve shown here are: 2. fan reversing valve solenoid (energized to reverse the flow of oil to the fan motor) 3. two crossover relief valves (used for fan motor anti-cavitation purposes) 4. two pilot operated reversing valves 5. main relief valve for the reversing fan circuit The status of the fan reversing valve solenoid may be viewed through the Advisor panel (Engine System Status screens) or through Cat ET.
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Text Reference
D8T POWER TRAIN COMPONENT IDENTIFICATION Power Train Oil Cooler
Engine Torque Divider
Torque Converter Outlet Relief Valve
Power Train ECM Remote Pressure Taps (TC In, TC Out, FW Lube)
Lube Distribution Manifold and Torque Converter Inlet Relief Valve
Power Train Oil Pump
Steering Differential
Torque Converter Charging Filter
Service Brakes
Priority Valve
Electronic Brake Valve
Transmission Charging Filter
Transmission Brake Pressure Test Ports
PT Oil Fill Tube and Dipstick Transmission Pressure Test Ports
Transmission Hydraulic Control
Bevel and Transfer Gears
Final Drives
58 POWER TRAIN Shown above is an illustration which identifies the relative location of all of the major power train components for the D8T Track-type Tractor. During this presentation, various colors are used to denote pressures within the systems. A legend outlining the meanings of this color code can be found in the back of this module. Numerous upgrades have been implemented in the power train for the D8T Track-type Tractor, as compared to the D8R Series II machine. The most prominent of these upgrades include: - the elimination of the transmission intermediate speed sensors - new transmission output speed sensors that are more reliable and easy to install; - elimination of transmission clutch engagement pressures, using the common top pressure strategy for the power train; - remote pressure test ports for all power train pressures; - relocation of the priority valve, for easier access; and - a new A4 Power Train ECM, which controls the transmission, the braking, and the steering.
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Text Reference
D8T POWER TRAIN ELECTRONIC CONTROL SYSTEM Left Brake
Lube Distribution Manifold and TC Inlet Relief Valve
Parking Brake Switch
Transmission Controls Advisor Steering Lever Position Sensors
Steering Differential
Instrument Cluster CAN C Data Link
Service Brake
Steering Motor Sensor
CAT Data Link CAN A Data Link Data Port
Brake Valve
Transmission Modulating Valves
3 4
2
Torque Converter
5 1
Crank Timing Sensor
Power Train Oil Cooler
Power Train Switches, Sensors, and Senders
CAN A Data Link
Engine ECM
CAT Data Link
Priority Valve Left and Right Steering Solenoid Valves
Power Train ECM
Right Brake
59 Power Train Electronic Control System The illustration above is a simplified schematic that shows all of the major hydraulic components and the major electronic components in the power train system. The The Power Train Electronic Control System consists of all the inputs to and outputs from the Power Train ECM, including the Power Train ECM. The Power Train ECM and its software, considers the input information, such as the service brake pedal position sensor, and controls the power train output components, such as the electronic brake control valve. If any of the controls or components are operating improperly or performing outside their operating parameters, the Power Train ECM will update the Caterpillar Monitoring and Display System, and Advisor will warn the operator or serviceman of the specific abnormal condition. For more information about accessing and viewing the status of the power train components, for instructions about how to change the parameters or the power train configuration, or for instructions on how to perform calibrations for any of the power train components, refer to STMG 790, "Caterpillar Monitoring and Display System, with Advisor™ for Track-type Tractors" (SERV1790).
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D8T POWER TRAIN SCHEMATIC
Left Brake Pressure Port
Left Brake Lube Pressure Port (LB1)
FIRST GEAR FORWARD Lube Distribution Manifold Flywheel Lube Pressure (L2) TC Inlet Relief Valve
Brake Pressure (B) Transmission Main Relief Valve
Steering Pump
Brake Valve
Pump Drive Lube
Vent Line
Transmission Main Relief Valve Pressure (P)
Clutch 4 2nd Clutch 3 3rd Clutch 2 FWD
Clutch 5 1st Clutch 1 REV
TC Inlet Relief Pressure (M)
TC Outlet Relief Pressure (N)
Transmission Lube
Suction Screen
Bevel Gear Lube
Scavenge Section "A"
TC Outlet Temp. Sensor
Flywheel Housing
C15 Engine 310 NET HP At 1850 RPM
T. C. Charge Section "B" TC Outlet Relief Valve
Transmission Charge Section "C" Transmission Lube Pressure (L1)
Priority Valve Pressure (PV) PTO Sump Temp. Sensor
Right Brake Pressure Port
Torque Converter
Right Brake Lube Pressure Port (LB2)
Torque Converter Charge Filter
Implement Pump
Power Train Oil Cooler
S•O•S Bypass Switch
Priority Valve
Transmission Charge Filter
Bypass Switch
60 Power Train Hydraulic System The three-section fixed displacement power train oil pump is mounted to the right front of the main case and is driven by a drive shaft connected to the rear of the implement pump. The transmission charging (C) section of the power train oil pump provides high pressure oil to the transmission main relief valve, which maintains a common top pressure for operation of the transmission modulating valves and the brakes. With the common top pressure power train strategy, transmission clutch engagement pressure calibrations and brake pressure adjustments no longer need to be performed. (Clutch fill time calibrations and brake touch-up calibrations are still required.) When the transmission main relief valve is properly adjusted, all of the pressures for the transmission clutches and for the brakes are also properly adjusted. The torque converter charging (B) section of the power train oil pump supplies oil to the torque converter, through the priority valve. Oil from the transmission charging section that flows past the main relief valve mixes with the lube oil from the power train oil cooler and is used to lubricate and cool the transmission and the bevel gears. The scavenge (A) section of the power train oil pump draws oil from the transmission and bevel gear case and from the torque divider housing and directs it to the sump in the main case.
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2
3
1 4
61 The torque converter inlet relief valve and the lube distribution manifold are located at the left front of the main case. They are consolidated into one dual purpose housing (1). The electronic brake control valve (2) is installed on top of the main case. The transmission charging section and the torque converter charging section of the power train oil pump draw their oil through the screened main sump suction manifold (3). The three-section power train oil pump (4) is located at the right front of the main case and it is driven by a shaft that connects to the rear of the implement pump (not pictured). This drive shaft is covered with a guard when the machine is completely assembled.
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5
Text Reference
4
6
1
3
2
62 The fixed displacement, three-section power train oil pump is mounted to the right, front of the main case. The power train oil pump scavenge section (1) draws oil from the transmission and bevel gear case (inside the main case). The scavenge section also draws oil from the torque divider housing (and lube oil from the flywheel housing) through the hose (5) on the left side of the pump. The oil from these two sources is pumped into the sump in the main case. The flow rate for the scavenge section of the power train oil pump is approximately 118 L/min (31.2 gpm). The torque converter charging section (2) and the transmission charging section (3) of the power train oil pump draw their oil from the main power train oil sump through the screened, main suction manifold (4). The screen in the suction manifold may be easily accessed by removing the square cover, on top of the manifold. The flow rate for the torque converter charging section of the power train oil pump is approximately 162 L/min (42.8 gpm). The flow rate for the transmission charging section of the power train oil pump is approximately 58 L/min (15.3 gpm). The pump drive hub (6) connects to a shaft that is driven by a similar hub at the rear of the implement hydraulic pump.
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7
6 5
8 4 3
9 2
1
63 The two, 6-micron power train oil filters and the priority valve are now located inside the forward compartment on the right fender. Shown in the illustration above is the torque converter charge filter (1) and the transmission charge filter (2). The priority valve (3) is integrated into the filter base/housing. The priority valve adjustment screw is located on the back side of the housing (not visible here), and opposite the priority valve solenoid (4). Accessible through the front compartment on the right fender are the following service points: 5. test port for transmission charge filter outlet pressure 6. test port for priority valve pressure/torque converter charge filter outlet pressure 7. test port for power train oil sampling (S•O•S)/torque converter charge filter inlet pressure 8. power train oil temperature sensor (main sump temperature) 9. bypass switch for the torque converter charge filter (The bypass switch for the transmission charge filter is located on the opposite side of this housing/filter base.) The status of the priority valve solenoid, the transmission oil temperature sensor, and both of the power train oil filter bypass switches may be viewed through the Advisor panel (Power Train System Status screens) or through Cat ET.
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Text Reference
D8T PRIORITY VALVE NORMAL MODE
Priority Valve and PTO Filter Base Check Housing Valve
To Brake Valve and Transmission
FLOW
Adjustment Screw
Solenoid Solenoid Valve Slug
Spring
Spool Cavity
Spool Assembly
From TC Charge Section of PTO Pump
To TC Inlet Relief Valve
Passage to Drain
64 The illustration above shows the priority valve in the Normal, or low pressure mode. The priority valve ensures that supply oil to the brake control valve and the transmission control group gets priority over supply oil to the torque converter circuit. The priority valve only operates at low pressure during certain conditions. In Normal Mode, oil from the torque converter charging section of the power train oil pump enters the slug chamber through a hole in the center passage of the spool and also enters the spool cavity through the solenoid valve and the connecting passage. The oil pressure on the left end of the spool causes the spool to shift to the right, against the spring. This allows the oil from the torque converter charging section to flow around the spool and out to the torque converter inlet relief valve. The pressure of the torque converter oil is lower than the pressure of the oil in the passage from the transmission charging section of the power train oil pump (going to the brakes and transmission). As a result, the check valve remains closed and the oil from the torque converter charging section of the power train oil pump does not mix with the oil from the transmission charging section. The coil of the solenoid valve is normally ENERGIZED when in the Normal Mode of operation. This strategy ensures that if communication is lost to the priority valve solenoid, the priority valve will default to the Priority Mode.
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Text Reference
D8T PRIORITY VALVE PRIORITY MODE
Priorit y Valve and PTO Filt er Base Housing
Check Valve
To Brake Valve and Transmission
FLOW
Adjustment Screw
Solenoid Solenoid Valve
Spring
Slug Spool Cavit y
Spool Assembly
From TC Charge Section of PTO Pump
To TC Inlet Relief Valve
Passage to Drain
65 The illustration above shows the priority valve operating in the Priority Mode. The priority valve operates in the Priority Mode under the following conditions: - power train oil (main sump) temperature less than 40°C (104°F) - engine speed below 1300 rpm - during transmission speed or directional changes During operation in the Priority Mode, the solenoid coil of the priority valve is DE-ENERGIZED. The solenoid valve then blocks torque converter charge oil from entering the spool cavity and allows the oil from the spool cavity to drain to tank. With only tank pressure at the left end of the spool, the spring shifts the spool back to the left. With the spool shifted to the left, only a small amount of torque converter charge oil can flow into the passage going to the torque converter inlet relief valve. With the passage to the torque converter mostly blocked, the pressure of the torque converter charge oil increases until it overcomes the combined force of the check valve spring and the pressure of the oil from the transmission charging section of the power train oil pump. As a result, the check valve opens and the flow of torque converter oil mixes with the transmission and brake oil. This ensures that there is enough oil to safely operate the transmission and brakes. The priority valve will default to Normal Mode when the parking brake is activated.
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NOTE: The priority valve strategy for operating in Normal Mode and in Priority Mode contains a "hysteresis band" for oil temperature and engine speed. The hysteresis band prevents the valve from rapidly shifting back and forth between modes when the threshold of any of controlling conditions are met. When engine rpms are increasing from low to high, the priority valve will remain in Priority Mode until the engine speed becomes greater than 1350 rpm. When engine rpms are decreasing from high to low, the priority valve will remain in Normal Mode until the engine speed becomes less than 1300 rpm. When the power train oil is cold, the priority valve will remain in Priority Mode until the power train sump oil temperature warms to greater than 45°C (113°F). When the power train oil is warm, the priority valve will remain in Normal Mode until power train oil temperature cools to below 40°C (104°F).
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3
Text Reference
1
2
4
5
6 8
7
66 Torque Divider The D8T Track-type Tractor uses a torque divider (1) to transfer engine power to the transmission. The torque divider is similar to those used on other Caterpillar Track-type Tractors except that the torque converter for the D8T is equipped with a freewheel stator. The torque divider provides both a hydraulic and a mechanical connection from the engine to the transmission. The torque converter provides the hydraulic connection, while the planetary gear set provides the mechanical connection. During operation, the planetary gear set and the torque converter work together to provide an increase in torque as the load on the machine increases. The illustration above shows the torque divider used in the D8T. The torque converter output speed sensor (2) is installed above the torque divider output shaft and senses the speed of the output shaft. The Power Train ECM monitors the signal from this sensor and uses it, along with the signal from the engine primary (crankshaft) speed/timing sensor to determine engine lug and shifting points for the Auto KickDown strategies. This signal is also used as one of the inputs to determine track speed, which is displayed on the LCD display in the instrument cluster.
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Torque converter charge oil from the torque converter inlet relief valve enters the torque converter through the torque converter inlet port (3), at the left side of the torque divider housing. A small amount of torque converter charge oil is used to lubricate the flywheel and the pump drive gears. This flywheel lube oil is directed to the flywheel housing through the small hose (4) at the left side of the torque converter inlet port (3). The small hose (5) installed at the right side of the torque converter inlet port leads to the remote pressure test tap for torque converter inlet pressure. The torque converter outlet relief valve (6) is located on the right side of the torque divider housing. The ecology drain for the torque divider housing (7) is located at the bottom center of the torque divider housing. The scavenge section of the power train oil pump draws oil from torque divider housing through the port (8) at the bottom center of the housing. The torque converter scavenge screen (not visible) is located just inside the hose flanges. Flywheel lube oil drains into the torque divider housing and is returned to the main sump by the scavenge section, also. The status of the torque converter output speed sensor may be viewed through the Advisor panel (Power Train System Status screens) or through Cat ET.
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Text Reference
TORQUE DIVIDER Engine Flywheel
Rollers
Housing Inlet Passage
Planet Gears
Springs Cam Freewheel Stator
Sun Gear Output Shaft
Planet Carrier
Carrier
Ring Gear
Outlet Passage Stator
Turbine
Impeller
67 This illustration shows a typical torque divider as used in the D8T. The impeller, the rotating housing, and the sun gear are shown in red. These components are on a direct mechanical connection to the engine flywheel. The turbine and the ring gear, shown in blue, are mechanically connected. The planetary carrier and the output shaft, shown in purple, are also mechanically connected. The stator and carrier are shown in green. The planetary gears and shafts are orange. The bearings and the lockup mechanism for the stator are shown in yellow. Because the sun gear and the impeller are connected to the flywheel, they will always rotate at engine speed. As the impeller rotates, it directs oil against the turbine blades, causing the turbine to rotate. Turbine rotation causes the ring gear to rotate. During NO LOAD conditions, the components of the planetary gear set rotate as a unit at the same rpm and the planet gears do not rotate on their shafts. As the operator loads the machine, the output shaft slows down. A decrease in output shaft speed causes the rpm of the planetary carrier to decrease. Decreasing the planetary carrier rotation causes the relative motion between the sun gear and the planet carrier to cause the planet gears to rotate. Rotating the planet gears decreases the rpm of the ring gear and the turbine. At this point, the torque splits with the torque converter multiplying the torque hydraulically and the planetary gear set multiplying the torque mechanically.
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Text Reference
An extremely heavy load can stall the machine. If the machine stalls, the output shaft and the planetary carrier will not rotate. This condition causes the ring gear and turbine to rotate slowly in the opposite direction of engine rotation. Maximum torque multiplication is achieved just as the ring gear and turbine begin to turn in the opposite direction. The torque divider is also equipped with a freewheel stator. The stator is splined to a cam which rotates around the stationary carrier in only one direction. Machined into the cam are tapered openings, each of which contain a roller and a spring. Spring force holds the roller against the taper and the carrier. This restricts the cam from turning. When the machine is under a load, and the impeller and turbine are rotating at different speeds, the stator is held stationary by the rollers being wedged in the taper of the openings by spring force. This mechanical connection keeps the stator stationary and allows oil flow to be directed back to the impeller, multiplying the torque. During all load conditions, the torque converter provides 70% of the output, and the planetary gear set provides the remaining 30% of the output. When the machine speed increases with no load, the speed of the turbine and impeller increases. During this condition the stator does not need to redirect oil back to the impeller. The stator begins to turn in the same direction as the impeller and the turbine. This moves the rollers from the tapered openings against spring pressure. The mechanical connection between the cam and the stationary carrier is broken. The stator, turning freely with the turbine and impeller, will reduce the turbulence of the oil in the torque converter. The lack of turbulence in the torque converter permits the engine to work easier, reducing fuel consumption and minimizing heat build-up in the power train oil system. When the machine is in a downhill situation and engine overspeed occurs, the Power Train ECM will automatically apply the service brakes, up to 8% of brake capacity, in an effort to slow the machine. If this strategy does not slow the engine enough, Advisor will warn the operator to change the mode of operation (down shift or apply the service brakes) to further slow the machine.
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Text Reference
1 4
2
3
68 The illustration above shows the dual purpose housing which contains the torque converter inlet relief valve manifold and the lube distribution manifold. This dual purpose housing is located at the left front of the main case. The torque converter inlet relief valve is a check valve (not visible above) that is pressed into a port on the front of the main case (see illustration 69). Torque converter oil enters the manifold from the back side, through a hard tube inside the main case. The torque converter oil exits the manifold (after the torque converter inlet relief valve) through the lower port (2). The torque converter oil is then directed to the torque converter inlet port, at the rear of the torque divider housing. The lube distribution manifold inlet (1) is the upper port on the dual purpose manifold body. Oil from the power train oil cooler is directed to the lube distribution manifold through the hose (3) connected to the upper port. The lube oil is then distributed to the brakes, the transmission, and the bevel gears through hard steel tubes inside the main case. The uppermost hose (4) is the connection between the main case sump and the power train oil high-speed oil change coupling, located in the left side engine compartment.
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Manifold
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To Torque Converter Inlet
Text Reference
D8T TORQUE CONVERTER INLET RELIEF VALVE
Front of Main Case Bottom of Main Case
Torque Converter Inlet Relief Valve From Priority Valve
To Main Sump
69 The torque converter inlet relief valve protects the components in the torque converter by limiting the maximum oil pressure to the torque converter. The torque converter inlet relief valve protects the torque converter when the engine is started and the oil is cold. Oil from the torque converter charge section of the power train oil pump is directed to the priority valve. From the priority valve, the torque converter oil is then directed to a passage at the front of the main case through a hard steel tube inside the case. The dual purpose manifold is installed on the front of the main case and directs the torque converter oil to the torque converter inlet relief valve through an internal passage in the manifold. The manifold also directs the torque converter oil to the torque converter through a hose connected to the front of the manifold. Torque converter oil pressure acts against the top of the poppet in the inlet relief valve. When the pressure acting against the top of the poppet overcomes the force of the spring, the poppet opens (down) and dumps the excess oil back into the main case, limiting the pressure in the torque converter circuit. The torque converter inlet relief valve is not adjustable.
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5
Text Reference
1 2
4
3
70 The torque converter outlet relief valve (1) is installed at the right rear of the torque divider housing. Torque converter oil exiting the torque converter enters the torque converter outlet relief valve from the back side of the valve body (1). The oil then exits the outlet relief valve and is directed to the power train oil cooler through the upper steel tube (2). After the oil passes through the oil cooler, it returns through the lower steel tube (3), where it is directed to the lube distribution manifold. The torque converter oil temperature sensor (4) is installed in the torque converter outlet relief valve. It senses the temperature of the oil exiting the torque converter and provides a signal to the Power Train ECM. Cat Advisor monitors this temperature data from the Power Train ECM and uses it to operate the torque converter oil temperature gauge (analog), at the upper right of the instrument cluster. The small hose (5) directs torque converter outlet relief pressure to the bank of three remote power train pressure taps. The status of the torque converter oil temperature sensor may be viewed through the Advisor panel (Power Train System Status screens and Performance 1 screen) or through Cat ET.
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Text Reference
TORQUE CONVERTER OUTLET RELIEF VALVE
Inlet Passage from Torque Converter
Spool
Shim
Outlet Passage to Power Train Oil Cooler
Spring
71 The torque converter outlet relief valve maintains a constant minimum pressure inside the torque converter. Oil from the torque converter enters the torque converter outlet relief valve through the inlet passage. The pressure of the oil acts against the top of the spool. When the pressure of the torque converter oil becomes greater than the force of the spring, the spool shifts down. Torque converter oil then flows through the holes around the circumference of the spool to the outlet passage. The outlet passage directs the hot torque converter oil to the power train oil cooler. The torque converter outlet relief valve may be adjusted by adding or removing shims between the spring and the spool.
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Text Reference
2
1 4
5 3
72 The power train oil cooler (1) is an oil-to-water type oil cooler. It is located at the right rear of the engine compartment. Oil from the torque converter outlet relief valve enters the cooler at the cooler inlet (2). The hot oil is cooled as it flows through tubes that are surrounded by engine coolant. The cooled oil then exits the power train oil cooler through the cooler outlet (3), where it is directed to the lube distribution manifold. Engine coolant flows from the water pump (4) to the engine oil cooler (5). After cooling the engine oil, the coolant then flows into the bottom of the power train oil cooler. The coolant flows up through the power train oil cooler, then exits the cooler and enters the engine block through a port (not visible) behind the power train oil cooler.
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Text Reference
1 4 5 2 3
6 7
73 Power Shift Transmission The planetary power shift transmission is capable of three speeds in FORWARD and three speeds in REVERSE. Power is transferred from the engine and the torque divider to the transmission through the input shaft (1). Power is transferred from the transmission to the transfer and bevel gears through the output shaft (2). The transfer and bevel gears transfer power to the final drives. The transmission contains three hydraulically controlled speed clutches and two hydraulically controlled directional clutches located in the planetary group (3). The transmission shifting function is controlled by the Power Train Electronic Control System. The The Power Train Electronic Control System consists of all the inputs to and outputs from the Power Train ECM, including the Power Train ECM. The Power Train ECM responds to shifting requests by controlling the electrical current to the solenoids of the transmission modulating valves (4). The transmission modulating valves control the hydraulic circuits that engage the transmission clutches. The Power Train ECM selects the transmission clutches to be engaged and the clutch pressure is modulated electronically. Transmission modulating valves control the flow of oil to and from the clutches. The Power Train ECM uses the transmission speed, the engine speed, and the power train oil temperature signals to control smooth engagement of the clutches.
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Text Reference
Each transmission clutch in the planetary group (3) has a corresponding solenoid controlled transmission modulating valve located on the transmission hydraulic control manifold (5). The Power Train ECM uses the transmission modulating valves to directly control the oil pressure to each transmission clutch. The modulating valves operate proportionally. The Power Train ECM sends an electrical current to the modulating valve solenoid. Electronic clutch modulation by the Power Train ECM controls the time required to fill a clutch with oil. Although clutch engagement pressure calibrations no longer need to be performed with the "common top pressure" power train strategy, clutch fill time calibrations are still required. The automated clutch fill time calibration procedure can be performed using Cat Advisor or by using Cat ET. This calibration routine "teaches" the Power Train ECM the length of time required for each clutch modulating valve to attain its clutch engagement pressure. The ECM applies current to the solenoid until the transmission output speed sensors detect a slight movement of the output shaft. When the output shaft begins to move, the ECM has "learned" and stored in memory the time required to pressurize the clutch to its engagement pressure. Transmission output speed and direction are sensed by the two transmission output speed sensors (6). The speed/direction pick-up wheel (7) is splined to the transmission output shaft. As the speed/direction pick-up wheel moves past the sensors, the wheel induces a current (signal) into each sensor. The difference in the timing between the signals of the two sensors determines the output shaft speed. Output shaft rotational direction is determined by sensing which sensor provides a signal first, then second. The signals from the sensors are monitored by the Power Train ECM. These signals are used by the Power Train Electronic Control System to modify the timing of clutch engagements. The status of all five transmission modulating valve solenoids may be viewed through the Advisor panel (Power Train System Status screens) or through Cat ET. NOTE: With the "common top pressure" strategy, clutch No. 1 (reverse direction), clutch No. 2 (forward direction), clutch No. 3 (speed 3), and clutch No. 4 (speed 2) operate at main relief pressure. Main relief pressure is approximately 2551 kPa (370 psi), at low idle (700 engine rpm) and with the transmission in NEUTRAL. At high idle, these same clutch pressures should be approximately 2758 kPa (400 psi), with the transmission in NEUTRAL. The Power Train ECM sends approximately 1.0 amp of current to these four transmission modulating valve solenoids to attain the clutch engagement pressure. Clutch No. 5 (speed 1) operates at a reduced pressure, which is approximately 2206 kPa (320 psi). The Power Train ECM regulates the pressure to the No. 5 clutch by sending a reduced current (approximately 0.7 - 0.8 amps) to the No. 5 transmission modulating valve solenoid.
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Text Reference
TRANSMISSION MODULATING VALVE ENERGIZED
Ball
Solenoid
Valve Spool
Orifice
Pin
Spring
Supply Oil from Pump To Clutch
74 The transmission clutches are hydraulically engaged and spring released. The transmission modulating valve solenoids are energized to send transmission charge oil to the clutches, as shown in the illustration above. As current is applied to the solenoid, the pin extends to the right and moves the ball closer to the orifice. The ball begins to restrict the amount of oil to drain through the orifice. This restriction causes the pressure to increase at the left end of the valve spool. As the pressure at the left end of the valve spool increases, the spool shifts to the right, closing off the passage from the clutch to the drain. At the same time, the movement of the valve spool to the right opens the passage from the pump supply to the clutch. This causes the clutch pressure to increase. De-energizing the solenoid decreases the force of the pin against the ball. This decreased force allows the pressure at the left end of the valve spool to unseat the ball, de-pressurizing the chamber at the left end of the spool. With no pressure at the left end of the spool, the valve spool shifts to the left due to the spring force plus the supply oil pressure. This condition reduces the pressure to the clutch by closing off the supply passage to the clutch and opening up the drain passage. When the pressure to the clutch falls below the clutch engagement pressure, the clutches will be released by spring force.
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Text Reference
When the transmission is in NEUTRAL, the transmission modulating valve that controls engagement of the No. 3 clutch allows flow to the clutch. The other modulating valves stop flow to the clutches, thereby allowing the clutches to be released by spring force. Since neither the No. 1 nor the No. 2 directional clutches are engaged, no power is transmitted to the output shaft of the transmission. When the transmission is in FIRST SPEED FORWARD, the modulating valves that control flow to the No. 2 and the No. 5 clutches receive a signal from the Power Train ECM. This signal energizes the solenoid which sends flow to engage the clutches. NOTE: Clutch Engagement Pressure Calibrations are no longer necessary due to the common top pressure strategy. However, transmission Clutch Fill Time Calibrations must be performed when any of the following repair procedures have been performed: -Transmission modulating valve and/or solenoid is replaced. -Transmission is serviced or replaced. -Power Train ECM is replaced. Transmission Clutch Fill Time Calibrations may be performed using Cat Advisor or by using Cat ET.
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Text Reference
D8T TRANSMISSION MAIN RELIEF VALVE Adjustment Screw
Spring
Spool
Slug Chamber
Slug
Locknut To Transmission Hydraulic Control
To PT Lube Circuit
From Trans. Charging Section of PTO Pump
75 The transmission main relief valve is located in the transmission hydraulic control manifold. The manifold is on top of the transmission planetary group. The transmission main relief valve maintains the "common top pressure" from the transmission charging section of the power train oil pump. This oil is used to operate the brakes and the transmission clutches. Oil to the main relief valve is supplied by the transmission charging section of the power train oil pump, when the priority valve is in the Normal Mode. If the priority valve is in the Priority Mode, the oil supply to the transmission main relief valve is a mixture of transmission charge oil and torque converter charge oil. Oil from the power train oil pump flows through the transmission charge oil filter and flows to the electronic brake control valve and the transmission modulating valves. The transmission main relief valve is downstream from the electronic brake control valve and the transmission modulating valves. The excess oil that flows over the main relief valve combines with the oil from the lube distribution manifold and is is used to lubricate the transmission planetary group. The transmission main relief pressure should be set to approximately 2550 kPa (370 psi), at Low Idle engine speed (700 rpm).
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Text Reference
POWER SHIFT TRANSMISSION
Ring Gears
Ring Gears Input Sun Gears
Input Shaft
Output Shaft Output Sun Gears
Planetary Carrier
2
3
4
5
76 This visual shows a sectional view of a typical transmission group like that used in the D8T Track-type Tractor. The planetary group has two directional and three speed clutches which are numbered in sequence (1 through 5) from the rear of the transmission to the front. Clutches No. 1 and No. 2 are the reverse and forward directional clutches. Clutches No. 3, No. 4, and No. 5 are the third, second and first speed clutches. The No. 5 clutch is a rotating clutch. In this sectional view of the transmission, the input shaft and input sun gears are shown in red. The output shaft and output sun gears are blue. The ring gears are shown in green. The planetary carrier is brown. The planet gears and shafts are shown in orange. The clutch discs, clutch plates, pistons, springs and bearings are shown in yellow. The stationary clutch housings are shown in gray. The input sun gears are splined to the input shaft and drive the directional gear trains. The output shaft is driven by output sun gears No. 3 and No. 4 and rotating clutch No. 5. When the No. 2, No. 3, or No. 4 clutches are engaged, their respective ring gears are held stationary. The No. 1 planetary carrier is held when the No. 1 clutch is engaged. When engaged, the No. 5 rotating clutch locks the output components (for FIRST gear) to the output shaft.
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Text Reference
4 5
3
1 2
77 Electronic Brake Control Valve The electronic brake control valve (1) is mounted to the top of the main case, situated below the operator seat. The brake control valve may be accessed by removing the operator seat, the seat pedestal, and the rear floor plate in the operator compartment. The brake valve body contains a proportional solenoid valve (2) which is controlled by a signal from a PWM rotary position sensor connected to the service brake pedal. The solenoid is normally energized when the brakes are released. Depressing the service brake pedal DECREASES the amount of current to the solenoid and de-energizes it to apply the brakes. The secondary brake valve is controlled by an ON/OFF solenoid (3). The ON/OFF solenoid is ENERGIZED by the secondary brake switch. The brake switch is a part of the service brake pedal and it is activated near the end of travel of the service brake pedal. An ON/OFF solenoid also controls the parking brake valve (4). The parking brake valve solenoid is energized when the operator activates the parking brake switch.
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Text Reference
The status of all three brake solenoids may be viewed through the Advisor panel (Power Train System Status screens) or through Cat ET. (The proportional service brake solenoid is designated as the "left brake" on the Advisor status screen and in Cat ET.) Brake pressure (B) at the brake control valve may be tested at the remote brake pressure port (5), located below the rear of the fuel tank. NOTE: The following information outlines the state of the three brake valve solenoids in the three possible conditions: Service Brakes Released - Proportional brake valve solenoid - ENERGIZED - Parking Brake valve solenoid - DE-ENERGIZED - Secondary brake valve solenoid - DE-ENERGIZED Service Brakes Applied (full) - Proportional brake valve solenoid - DE-ENERGIZED - Parking Brake valve solenoid - DE-ENERGIZED - Secondary brake valve solenoid - ENERGIZED Parking Brake Applied - Proportional brake valve solenoid - DE-ENERGIZED - Parking Brake valve solenoid - ENERGIZED - Secondary brake valve solenoid - ENERGIZED
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Text Reference
D8T ELECTRONIC BRAKE CONTROL VALVE ENGINE ON / BRAKES RELEASED
Parking Brake Solenoid Valve and Secondary Brake Solenoid Valve
Parking/Secondary Brake Valve
Parking/Secondary Brake Valve Pilot Chamber Reducing Spool
Accumulator Piston Pilot Valve
Pressure Feedback Chamber Orifice
Accumulator Chamber Proportional Solenoid Valve
Pilot Pressure Chamber
Slot Holes Shutoff Spool
To Brakes
Supply Oil from Pump
Shutoff Valve
78 The proportional solenoid valve for the service brakes is controlled by the Power Train ECM. The solenoid valve is ENERGIZED to release the brakes. The Power Train ECM determines the amount of current to the solenoid by the position of the service brake pedal. When the proportional solenoid (valve) is energized, the pilot valve is closed. This allows pump supply oil to pressurize the pilot pressure chambers at the proportional solenoid valve, the parking brake valve and the secondary brake valve, and in the accumulator chamber. As the accumulator chamber pressure increases, the reducing spool moves to the right against the spring, closing off the drain passage. At the same time, the passage to the brakes is opened to the passage from the pump supply oil. Pressure then builds in the pressure feedback chamber and the passage to the brakes. As the pressure increases, the spring applied brakes are released. When the operator depresses the service brake pedal, the PWM sensor attached to the service brake pedal sends a signal to the Power Train ECM. The Power Train ECM then decreases the current to the proportional solenoid at a rate that is directly proportional to the movement of the pedal. As the solenoid is DE-ENERGIZED, the pilot valve opens and allows the pump supply oil in the pilot pressure chamber to drain to tank. This reduces the pressure in the pilot pressure chamber at the solenoid valve. The accumulator chamber and the parking/secondary brake valve pilot chamber are also reduced by draining through the holes in the shutoff spool.
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Text Reference
As the pilot pressure at the left end of the shutoff spool decreases, the pilot pressure at the right end of the shutoff spool moves the spool to the left, against the spring. When the spool moves all the way to the left, the holes in the spool are opened to drain due to the slot that is machined in the shutoff valve. The pressures in the accumulator chamber and the parking/secondary brake valve pilot chamber are now allowed to drain through the holes in the spool. As the pilot pressure decreases, the spring begins to move the shutoff spool back to the right. As the shutoff spool moves back to the right, the holes in the spool are covered again by the right end of the shutoff valve. This reduces the rate of reduction in pilot pressure, allowing the brakes to be slowly applied. The pilot oil can then only escape by flowing between the outer diameter of the shutoff spool and the inner diameter of the shutoff valve, and then through the holes in the shutoff spool. As the pilot pressure slowly decreases, the spring moves the shutoff spool further to the right until the holes in the spool are uncovered again at the right end of the shutoff valve. The remainder of the pilot pressure then completely drains to tank through the shutoff spool. As the pilot pressure decreases, the combined force of the reducing spool spring and the pressure in the feedback chamber moves the reducing spool to the left. The accumulator piston acts as a cushion and aids in preventing the reducing spool from moving too rapidly. As the reducing spool moves to the left, the pump oil supply passage to the reducing spool is closed off. At the same time, the tank passage to the reducing spool is opened, allowing the pressure oil in the brakes to drain to tank. As the pressure to the brakes decreases, the Belville springs begin to engage the brakes. If the operator depresses the service brake pedal completely, the secondary brake switch is activated. The secondary brake switch makes a direct connection between the battery and the secondary brake valve solenoid, which ENERGIZES the secondary brake solenoid. Also, when the parking brake switch is set to the ON position, the parking brake valve solenoid is connected directly to the battery, which ENERGIZES the parking brake solenoid. As a backup measure, the secondary brake solenoid is also ENERGIZED when the parking brake switch is set to the ON position. Energizing either the parking brake or the secondary brake solenoids completely drains all pilot pressure oil, resulting in all the oil being drained from the brakes, resulting in full engagement of the brakes. NOTE: There are no longer any check valves installed in the brake valve body between the reducing spools and the secondary or parking brake valves. These check valves serve no purpose in differential steer machines. These check valves are present, however, in brake valves used on Finger Tip Control machines. They serve to isolate the left brake and right brake passages from each other, for steering purposes.
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Text Reference
BRAKE CONTROL VALVE SERVICE BRAKES RELEASED Proportional Brake Solenoid
Pressure Reducing Spool (Left Brake)
Parking Brake Solenoid
To Right Brake
To Left Brake
Pressure Reducing Spool (Right Brake)
Pump Supply
Secondary Brake Solenoid
79 The illustration above, and those on the next two pages show the electronic brake valve as if it had been sliced in half, horizontally, with the upper half laid over to the right. The lines in the illustration represent the internal passages of the brake valve as they would normally be connected. Illustration 79 shows the electronic brake valve with the brakes released. When the operator releases the service brake pedal, the PWM rotary position sensor (connected to the brake pedal) sends a signal to the Power Train ECM. The Power Train ECM then increases the current to the (proportional) brake solenoid. The amount of current sent to the solenoid is directly proportional to the position of the service brake pedal. The increased current to the solenoid closes the poppet in the solenoid valve which closes off the flow of pump supply oil to drain. The result is increased pilot pressure to both pressure reducing spools. This increased pressure moves the reducing spools downward. As the spools move downward, the flow of supply oil is shut off to the drain passage and the supply oil then flows into the brake passage and out to the brakes. This increased pressure releases the brakes against the brake (Belville) springs.
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Text Reference
BRAKE CONTROL VALVE SERVICE BRAKES ENGAGED
Proportional Brake Solenoid
Pressure Reducing Spool (Left Brake)
Parking Brake Solenoid
To Right Brake
To Left Brake
Pressure Reducing Spool (Right Brake)
Pump Supply
Secondary Brake Solenoid
80 Illustration 80 shows the electronic brake valve when the brakes are fully engaged. When the operator depresses the service brake pedal, the PWM rotary position sensor (connected to the pedal) sends a signal to the Power Train ECM. The Power Train ECM then decreases the current to the proportional (service) brake solenoid. The amount of current sent to the solenoid is directly proportional to the position of the service brake pedal. The decreased current to the solenoid opens the poppet in the solenoid valve and opens the flow of pump supply oil to drain. The result is decreased pilot pressure to both pressure reducing spools. This decreased pressure allows the springs below the reducing spools to move the reducing spools upward. As the spools move upward, the passage from the brakes is connected to the drain passage, which decreases the pressure to the brakes. This decreased pressure allows the brake (Belville) springs to begin engaging the brakes. When the operator completely depresses the service brake pedal, the secondary brake switch is activated. The secondary brake switch then connects the battery to the secondary brake solenoid. The ENERGIZED secondary brake solenoid valve completely dumps the pilot pressure to tank, which causes the reducing spools to move upward. As the spools move upward, the passage from the brakes is connected to the drain passage, which decreases the pressure to the brakes and the brakes are fully engaged.
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Text Reference
BRAKE CONTROL VALVE PARKING BRAKES ENGAGED
Proportional Brake Solenoid
Pressure Reducing Spool (Left Brake)
Parking Brake Solenoid
To Right Brake
To Left Brake
Pressure Reducing Spool (Right Brake)
Pump Supply
Secondary Brake Solenoid
81 Illustration 81 shows the electronic brake valve when the parking brakes are engaged. When the operator pulls the parking brake switch UP, the switch is activated. The parking brake switch connects the parking brake solenoid to the battery and the solenoid is ENERGIZED. The secondary brake solenoid is also ENERGIZED by the Power Train ECM as a backup safety measure. The parking brake and secondary brake valves completely dump the pilot pressure to tank, which causes the reducing spools to move upward. As the spools move upward, the passage from the brakes is connected to the drain passage, which decreases the pressure to the brakes. This decreased pressure allows the brake (Belville) springs to begin fully engage the brakes.
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Text Reference
1 2
82
3
83
6
4 5
Located at the rear of the forward compartment on the right fender, and just ahead of the hydraulic oil tank is the power train oil fill tube (1) and dipstick (2). The power train breather (3) is installed on the side of the power train oil fill tube. Removing the triangular deck cover (two bolts) just outside the right door to the operator compartment gains access to the following remote pressure test ports: 4. torque converter outlet relief pressure (N) 5. torque converter inlet relief pressure (M) 6. flywheel lube pressure (L2)
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5 4
Text Reference
3 2 1 84
85 8
7
6
The five transmission clutch pressure test ports accessible from the rear of the machine are: 1. 2. 3. 4. 5.
clutch #1 (reverse) clutch #2 (forward) clutch #3 (speed 3) clutch #4 (speed 2) clutch #5 (speed 1) (rotating clutch)
The following pressure test ports are located at the top of the transmission case: 6. transmission lube pressure (L1) 7. transmission main relief pressure (P) The remote pressure test port (8) for brake pressure (B) is installed in the bracket at the top of the transmission case, just below the fuel tank.
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Text Reference
1 2
86
4
87 3
Brake pressure for the right brake may be tested by removing the plug (1) and installing a pressure test tap. Brake lube pressure (LB2) may be tested in a like manner at the forward port (2). The test ports for left brake pressure and left brake lube pressure (LB1) are reversed. At High Idle, with the brakes RELEASED and the transmission in NEUTRAL, the brake lube pressure should be approximately 140 kPa (20 psi). At High Idle, with the brakes ENGAGED and the transmission shifted to THIRD SPEED FORWARD (3F STALL - approximately 1520 engine rpm), the brake lube pressure should be approximately 70 kPa (10 psi). The service brake pedal (3) is connected to a rotary position sensor (4) that sends a PWM signal to the Power Train ECM, which in turn controls the proportional solenoid for the service brakes. The status of service brake pedal position sensor and the secondary brake switch may be viewed through the Advisor panel (Power Train System Status screens) or through Cat ET.
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Text Reference
88
If equipped, the High-Speed power train oil connection (arrow) is located inside the left side engine compartment door, near the front of the engine compartment.
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Text Reference
FINAL DRIVE, BRAKE GROUP, AND STEERING DIFFERENTIAL AND PLANETARY Sprocket Segments Outer Planetary Gears
Inner Planetary Gears
Brake Housing
Brake Oil Discs and Plates Supply Passage
Housing
Steering Pinion
Hub Inner Sun Gear
Ring Gear Carrier Planet Gears
Outer Axle Shaft
Center Axle Shaft Sun Gears
Outer Sun Gear Outer Carrier
Ring Gear Carrier Bevel Gear Hub
Duo-cone Seals Piston
Ring Gear
Inner Carrier
Brake Pressure Chamber Belville Spring
89 DIFFERENTIAL STEER MECHANICAL OPERATION This left side sectional view shows the final drive, the brake group, and the steering differential and planetary. Power from the transmission is transmitted from the steering differential (purple) and the center axle shaft (yellow) to the brakes (dark yellow) and to the final drive through the outer axle shaft (yellow). The final drive components consist of the following: -
Outer planetary gears (green) Outer sun gear (green) Outer carrier (green) Ring gear (gray) Inner planetary gears (blue) Inner sun gear (blue) splined to the outer axle shaft Inner carrier (blue) Sprocket segments and hub (brown)
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Text Reference
The rotation of the outer axle shaft and the inner sun gear causes the inner planet gears to turn. The ring gear is stationary. As the inner planet gears rotate around the inside of the ring gear, the inner carrier turns. The inner carrier is connected to the outer sun gear by splines. As the inner carrier rotates, the outer sun gear causes the outer planet gears to turn. The outer planet gears move around the inside of the ring gear causing the outer carrier and hub to turn. Power is then directed to the sprocket segments and the track. All of the components in the final drive are splash lubricated from oil inside the final drive. The brake components (dark yellow) consist of the following: -
Brake housing Discs and plates Piston Belville spring Spool
The brakes are used only to stop the machine and do not assist in steering. Pressure oil from the electronic brake valve releases the brake by moving the brake piston to the right. Belville springs are used to compress the plates and discs, which applies the brakes. When the service brake pedal is depressed, brake pressure is drained from the brake pressure chamber. The Belville springs then compress the plates and discs, which stops the rotation of the outer axle, the final drive components and the hub and sprocket segments. The machine will come to a complete stop. The steering differential and the planetary components (purple) consist of the following: -
Housing Bevel gear Steering pinion Two ring gears Planet gears Two carriers Two sun gears
The left side of the differential receives transmission power from the center axle shaft. During steering, power is also supplied by the steering motor through the steering pinion and bevel gear. The steering pinion and bevel gear are connected to the housing which is splined to the ring gear. The planet gears are connected to the carrier, which is splined to the outer axle shaft. The hub (gray) is stationary and uses a Duo-cone seal to keep contaminants out of the housing.
WARNING When warming the power train oil by stalling the torque converter at high idle, ensure that the transmission is shifted to THIRD SPEED FORWARD and the service brakes are fully applied. Be aware that the machine WILL MOVE against the brakes if the transmission is shifted to FIRST GEAR FORWARD and the engine is set to high idle.
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Text Reference
D8T DIFFERENTIAL STEERING SYSTEM NO TURN
Pump Control Spool HD Steering Motor
Steering Control Valve
Pump Actuator Piston
Crossover Relief Valves
Steering Pump
Charge Pump
Power Train ECM
Flushing Valve
HC
To Case Drain Filter
X1
X2
Charge Pressure Relief Valve
Pressure Override Valve
Cold Oil Relief Valve
Steering Charge Filter From Hydraulic Tank Fluid Sampling
Suction Manifold
To Demand Fan Pump
Pilot Supply To Dual Tilt Valve Steering Control Lever
Steering Lever Position Sensors From Hydraulic Oil Cooler
90 Differential Steering System Operation The steering system for the D8T Track-type Tractor has been upgraded to an electronically controlled differential steering system. These upgrades include: - solenoid controlled over-center bi-directional piston pump - steering control lever using three rotary position sensors (triple redundant signal) - bent axis steering motor with speed and direction sensor - steering system controlled by the power train ECM Shown above is a schematic of the steering hydraulic system for the D8T in the NO TURN (NO STEER) condition. The gear-type charge pump and the over-center bi-directional steering pump operate similar to the steering pump on the current D8R Series II Track-type Tractor, except that the steering pump is controlled by two solenoid valves. (The D8R Series II used a pilot operated pump control valve to control the steering pump.) Also, the D8T steering control lever (tiller) uses three rotary position sensors to send a signal to the pump control solenoid valves through the Power Train ECM, instead of the mechanically operated pilot valve used in the D8R Series II machine. The steering motor is similar to that used on the current D8R Series II, but now it utilizes a dual Hall Effect sensor in order to provide speed and direction output information to the Power Train ECM.
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Steering System Components The major components of the steering system are: Charge pump: The charge pump fills the system with oil during start-up and provides oil for the drive loops and pilot oil for the steering control valve. Charge pressure is maintained by the charge pressure relief valve and is set to approximately 2930 kPa (425 psi) at high idle. (On machines equipped with dual tilt, charge oil is also used as pilot oil for the operation of the dual tilt valve.) Pressure override (cutoff) valve: When the pressure in either side of the steering loop reaches approximately 40160 kPa (5825 psi), the pressure override (POR) valve opens and destrokes the pump by draining the charge pressure sent to the steering control valve, which is used to move the pump actuator piston. Charge pressure relief valve: The charge pressure relief valve limits the charge pressure to approximately 2850 kPa (413 psi) at 2000 rpm. Charge oil is then sent to the drive loop, the steering control valve, and the pump actuator piston. Crossover relief and makeup valves: Each side of the drive loop has a crossover relief and makeup valve that limits the pressure spikes in either side of the drive loop. These valves also direct the charge pressure through an internal check valve that opens to fill the low pressure side of the drive loop. Pump control spool and pump actuator piston: The steering pump control spool is contained in the pump control valve. The pump control spool is moved by the pump control solenoids. The pump control spool directs charge pressure to the left or to the right end of the pump actuator piston. As the pump actuator piston moves, it changes the angle and/or direction of the swashplate. The feedback lever in the pump control valve follows up to move the pump control spool back against the pump control solenoid. This ensures that the correct pressure is metered to the pump actuator piston for the amount of steering flow requested. In the NEUTRAL (or NO STEER) position, reduced charge pressure is present at each end of the pump actuator piston. Steering lever position sensors: Three (triple redundant) PWM rotary position sensors are attached to the shaft of the steering control lever (tiller). The position sensors send PWM signals to the Power Train ECM. The PWM signals reflect the position of the steering tiller. The Power Train ECM then sends current to either the left or the right steering pump control solenoid, which moves the pump control spool. Steering pump control solenoids: The steering pump control solenoids (left and right) are installed in the steering control valve and are energized by the Power Train ECM. The Power Train ECM determines the amount of current and which pump control solenoid to energize based on the signals received from the steering lever position sensors. As the solenoids are energized, the solenoid pin pushes against the end of the pump control spool.
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Power Train ECM: The Power Train ECM receives PWM signals from the steering lever position sensors and sends a corresponding current to the appropriate steering pump control solenoid. The pump control solenoid moves the pump control spool, which in turn, controls the flow and the direction of the oil in the steering system. Steering motor with flushing valve: Flow from the steering pump turns the steering motor clockwise or counterclockwise, resulting in either left or right turns. A flushing valve is contained in the control plate of the steering motor. The flushing valve meters oil from the low pressure side of the steering loop to case drain, to help keep the motor cool during operation. Steering charge filter and bypass switch: The spin-on steering charge filter with a bypass valve ensures that clean charge oil is delivered to the steering system. The filter is located in the forward compartment on the right fender and is positioned in-line between the charge pump and the steering piston pump. The normally open bypass switch is monitored by the Power Train ECM. The bypass switch is installed in the charge filter inlet passage and held closed by the bypass valve. When the bypass valve opens, allowing oil to flow around the filter, the switch also opens and Cat Advisor alerts the operator that the steering charge filter is being bypassed. Cold oil relief valve: The cold oil relief valve protects the charge circuit when the oil is cold. The cold oil relief valve opens at approximately 3200 kPa (465 psi), at a flow rate of 1.0 L/min (.26 gpm) when the oil is cold. This valve is installed in the main hydraulic suction manifold. When it opens, the oil is vented directly into the hydraulic suction manifold.
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6
8
9 10
5 11 4
3 2
1
91 The steering pump (1) is mounted to the upper left, and at the rear of the flywheel housing. It is driven by a gear inside the flywheel housing. The high pressure steering loop hoses (7) direct high pressure steering pump discharge oil to the steering motor (5). The steering motor is installed at the left front of the main case. The smaller hose (2) directs steering charge pressure to the suction manifold. When the oil is cold, or when there are pressure spikes in the steering charge pressure circuit, the cold oil relief valve (3) will open, allowing the charge oil to be vented into the suction manifold. Left steering loop pressure (HC) may be checked at the lower pressure test port (4) on the steering motor. Right steering loop pressure (HD) may be checked using the upper pressure test port (6) on the steering motor. Other service points shown above are: 8. pump control solenoid "A" (right steer) 9. pump control solenoid "B" (left steer) 10. left steer actuator pressure test port (X2) 11. right steer actuator pressure test port (X1)
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D8T STEERING LEVER POSITION SENSORS Sensor No. 3 Sensor No. 2 Sensor No. 1
12 Pin Connector
92 The illustration above shows the steering control lever with the steering lever position sensor assembly attached to the steering lever shaft. The three PWM sensors are a single component. If one sensor fails, the component (all three sensors) must be replaced. When the operator moves the steering control lever, these sensors send a PWM signal to the Power Train ECM. The Power Train ECM then sends a corresponding signal to the appropriate proportional steering pump control solenoid. The pin of the steering pump control solenoid comes into contact with, and moves the pump control spool. When properly calibrated, all three sensors should send a PWM signal of approximately 50% of duty cycle in the NO STEER condition. In the full LEFT STEER condition, the sensors should send approximately 8% of duty cycle. In the full RIGHT STEER condition, the sensors should send approximately 92% of duty cycle. The signal from all three steering position sensors must agree with each other within a certain percentage, or Advisor will warn the operator of a steering failure. The sensors must be recalibrated if this condition occurs. If recalibration does not correct the problem, the sensors must be replaced.
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The status of all three steering lever position sensors may be viewed through the Advisor panel (Power Train System Status screens) or through Cat ET. A calibration routine for these "Steering Control Position Sensors" may performed through Cat Advisor, or by using Cat ET. The steering lever position sensors and pump control solenoids replace the steering pilot valve and the pilot operated pump control valve used in the D8R Series II Track-type Tractor.
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3
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2
1
93 The steering charge filter (1) is located in the forward compartment on the right fender. The filter base for the steering charge filter contains the following service points: 2. a combination test port for testing charge pump discharge pressure (F) and the hydraulic system fluid sampling (S•O•S) port 3. the steering charge filter bypass switch (pressure differential switch) 4. the charge pump discharge pressure sensor The status of the steering charge filter bypass switch and the charge pump discharge pressure sensor may be viewed through the Advisor panel (Power Train System Status screens) or through Cat ET.
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1
94 2
DUAL HALL EFFECT SPEED AND DIRECTION SENSOR Hall Effect Element No. 1
95
Hall Effect Element No. 2
The steering motor (1) is located at the left, front of the main case. It provides input to the steering differential. A dual Hall Effect speed and direction sensor (2) is installed in the port on the left side of the steering motor. The dual Hall Effect sensor contains two sensing elements. As the steering motor rotates, the rotation of the internal parts of the motor induce a current (signal) into both elements in the sensor. The difference in the timing between the signals determines motor speed. Direction is determined by sensing which element provides the signal first, then second.
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Text Reference Dual Hall Effect Speed Sensor
D8T STEERING MOTOR LEFT TURN
Case Drain Port Piston
Output Shaft
Barrel Head
Control Plate Flushing Valve Steering Pump
Flushing Valve Pin Case Drain Port From Steering Pump
To Steering Pump
To Steering Pump
Return to Tank
From Steering Pump
96 The illustration above shows the 40° bi-directional bent-axis piston-type steering motor and the flushing valve in the LEFT TURN condition. The flushing valve permits oil to flow from the low pressure side of the loop through the valve when a right or left turn is initiated. Two sources of cooling oil are provided to the motor. The first source is the internal flushing valve in the control plate The second source is the steering pump case drain oil that is routed to the steering motor case. The flushing valve is contained within the control plate of the steering motor. This valve is designed to drain approximately 4 L/min (1 gpm) of flow from the motor when the steering loop pressure increases to 2500 kPa (363 psi). When the pressure in the drive side of the loop is 2500 kPa (363 psi) higher than the return side, the higher pressure moves the pin and allows oil to flow through the control plate into the motor case. This oil combines with the steering pump case drain oil for additional cooling. The combined flow is directed back to the tank. (A case drain manifold is located on the front of the main case. All pump and motor case drain lines converge at this manifold, which then returns all case drain oil to the hydraulic tank, through the case drain filter.)
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1
2 3 97
5 6 4 98
The steering pump (1) is mounted to the upper left, rear of the flywheel housing. Components of the steering pump are identified above. These components are: 2. crossover relief valves 3. charge pressure relief valve 4. pressure override valve 5. pump actuator mechanical adjustment screw 6. charge pump
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D8T STEERING PUMP - SIDE VIEW LEFT TURN
Pump Control Solenoid
Pump Control Valve Right Crossover Relief Valve
Feedback Lever Pump Actuator Piston
From Steering Motor
Input Shaft
Swashplate Charge Pump Piston
Barrel
To Steering Motor Left Crossover Relief Valve
99 The illustration above shows a cut-away side view of the steering pump. Visible in this illustration are the following components: - charge pump - crossover relief valves - pump control valve - pump control solenoid - feedback lever - pump actuator piston - input shaft - swashplate - piston - barrel
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D8T STEERING PUMP END VIEWS LEFT TURN
Pressure Override Valve
Steering Loop
Crossover Relief Valve
Filter
Charge Pump
Resolver
Charge Pressure Relief Valve Steering Loop
Crossover Relief Valve
100 This visual shows the steering pump during a LEFT TURN. The left crossover relief valve is closed and the drive (high pressure) loop pressure (red) is sent to the steering motor. The right crossover relief valve is in the makeup mode, allowing charge pressure oil (orange) to replenish the return side of the steering loop. If a pressure spike occurs in the drive side of the loop, the left crossover relief valve opens and directs excess oil into the return side of the loop. If the drive loop pressure exceeds the pressure override valve (POR valve) setting, the highest resolved steering loop pressure opens the POR valve. When the POR valve opens, it destrokes the pump by draining the charge pressure oil (orange) that is sent to the pump control spool and the pump control piston. An orifice (not visible) between the charge pressure relief valve and the POR valve helps maintain the charge pressure to the crossover relief valves when the POR valve drains charge oil from the pump control spool and from the pump actuator piston. The charge pressure relief valve limits the charge pressure (orange) used in the steering system and continually drains the excess oil that is not required in any of the circuits.
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D8T STEERING PUMP TOP VIEW LEFT TURN
Pump Control Solenoid
Notch
Pin
Lever Arms
Pump Actuator Piston
Feedback Lever
Pivot Point
Pump Control Spool
Retention Pin
101 The pump control spool directs reduced pressure charge oil (orange and white stripes), to control the pump actuator piston. The movement of the pump control spool is approximately 2.00 mm (.078 in.) in each direction. This spool constantly meters the charge oil to maintain the correct pressure at the pump actuator piston, which maintains the correct swashplate angle. This illustration shows the pump control spool moved to the LEFT TURN position by the pump control solenoid. The proportional pump control solenoid is ENERGIZED in direct proportion to the amount of steering control lever (tiller) movement. As the pump control solenoid is ENERGIZED, the solenoid pin moves the pump control spool down, which opens a passage that sends charge pressure oil to the upper end of the pump actuator piston. As the pump actuator piston moves down, the feedback lever shifts the upper lever arm. This movement increases the tension of the compression spring proportional to the force created by the solenoid pin against the pump control spool. The tension on the spring pulls the lower lever arm up. The lower lever arm pushes against the retention pin, which forces the pump control spool back up, against the solenoid pin. These two forces balance each other, and meter the flow of charge oil to the actuator piston.
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The lever arms and the feedback lever pivot on an eccentric adjustment screw. The adjustment screw can be used to change the center position of the spool. Changing the center position of the spool also changes the pivot point of the feedback lever and the lever arms. When the pump control spool is properly adjusted (centered) the charge pressure at either end of the actuator piston (X1 and X2) will be equal. The charge pressure oil directed to the upper end of the pump control piston compresses the large springs and moves the pump actuator piston down. The piston is mechanically connected to the swashplate. When the pump actuator piston moves down, the angle of the swashplate is increased, which increases the flow of oil to the steering motor. If the operator stalls the steering motor, the POR valve destrokes the pump by draining charge pressure oil from the pump actuator piston. The large springs in the pump actuator piston move the piston up and the swashplate toward minimum angle to reduce pump output. This condition occurs automatically and prevents the operator from stalling the steering system at maximum flow. If the operator holds the tiller at the full left turn position with the brakes engaged, the crossover relief valve will limit the drive loop pressure and the POR valve will drain the charge pressure oil from the upper end of the actuator piston, decreasing the angle of the swashplate. Pump flow is at minimum, but the system pressure is at the setting of the POR valve. The status of the steering pump control solenoids may be viewed through the Advisor panel (Power Train System Status screens) or through Cat ET. NOTE: In NEUTRAL (no turn), the pump control spool (if properly centered) will send equal pressure to each end of the pump actuator piston. Since 600 kPa (87 psi) is needed to move the pump actuator piston, a difference of more that 600 kPa (87 psi) will cause the machine to move when the parking brake switch is set to the released position. If the eccentric adjustment screw for the pivot point of the feedback lever and and the lever arms needs adjustment, follow the procedure in the System Operation, Test and Adjust for the Hydraulic System (Form RENR7527). Before making any adjustments to the eccentric adjustment screw, ensure that the steering lever position sensors and the steering pump control solenoids are calibrated. Cat Advisor or Cat ET can be used to calibrate these solenoids.
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D8T DIFFERENTIAL STEERING SYSTEM LEFT TURN
Pump Control Spool HD Steering Motor
Steering Control Valve
Pump Actuator Piston
Crossover Relief Valves
Steering Pump
Charge Pump
Power Train ECM
Flushing Valve
HC
To Case Drain Filter
X1
X2
Charge Pressure Relief Valve
Pressure Override Valve
Cold Oil Relief Valve
Steering Charge Filter From Hydraulic Tank Fluid Sampling
Suction Manifold
To Demand Fan Pump
Pilot Supply To Dual Tilt Valve Steering Control Lever
Steering Lever Position Sensors From Hydraulic Oil Cooler
102 This illustration shows the steering system during a LEFT TURN. The steering control lever has been moved to the LEFT STEER position, causing the steering lever position sensors to send a signal to the Power Train ECM. The Power Train ECM responds by sending a current to the left pump control solenoid. As the solenoid is ENERGIZED, the solenoid pin pushes against the left end of the pump control spool, which directs charge pressure oil to the pump actuator piston. The actuator piston mechanically moves the swashplate to the desired pump angle. Steering pump flow is then sent to the steering motor which provides a mechanical input to steer the machine to the left. As the pressure increases in the drive side of the steer loop, the left crossover relief valve closes. The right crossover relief valve opens and lets charge pressure oil flow into the return side of the steering loop to provide makeup oil and replenish leakage in the loop. During a stall condition, the pressure spike which occurs in the drive side of the loop is relieved by the crossover relief valve and sent to the return side of the loop. If the operator continues to hold the tiller in the same position, the POR valve opens and drains the oil sent by the pump control spool to the pump actuator piston. The piston causes the swashplate to move toward a minimum angle and maintain maximum pressure. NOTE: Charge pressure (orange) and low pressure return oil (red and white stripes) are equal. The respective flows are shown this way to help keep the circuits separate.
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D8T IMPLEMENT HYDRAULIC SYSTEM Ripper Lift Cylinder
Blade Tilt Cylinder
Pressure Reducing Manifold
Ripper Tip Cylinder
End Cover Ripper Tip Control Valve Ripper Lift Control Valve Blade Tilt Control Valve Blade Lift Control Valve
Ripper Tip Cylinder
Ripper Lift Cylinder
Implement Control Valves
Blade Lift Cylinder
Blade Lift Cylinder
Inlet Manifold
Hydraulic Tank
Implement Return Line
Implement Supply Line
Blade Tilt Cylinder
Pump Compensator Valve
Implement Pump
Signal Line
103 IMPLEMENT HYDRAULIC SYSTEM The implement hydraulic system for the D8T contains the following components: - a load sensing, pressure compensated, variable displacement piston pump; - electro hydraulic implement control valves (pilot operated/solenoid controlled), a pilot manifold, and a pilot filter, all combined in one assembly and located in the notch of the fuel tank; - electronic implement controls with an A4 Implement ECM; - filters for steering charge circuit oil, case drain oil, and pilot supply oil; and - an oil-to-air hydraulic oil cooler mounted behind the radiator cores; The differential steering system and the hydraulic demand fan system are both connected to the implement system and all three systems use the same hydraulic oil. However, the steering system is controlled by the Power Train ECM and the fan system is controlled by the Engine ECM. These steering and fan systems are explained in other sections of this module. The status of all sensors and solenoids may be viewed through the Advisor panel (Implement System Status screens) or through Cat ET.
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3 2 1 4
5
8
6 7
104 The hydraulic tank (1) is mounted on top of the right fender, just ahead of the right rollover support post. The hydraulic tank serves as a reservoir that provides oil for the operation of the implements, the hydraulic demand fan, and the steering pump. Components and service points for the hydraulic tank shown in the above illustration are: 2. vacuum breaker 3. hydraulic case drain filter access (one, 6-micron filter) 4. hydraulic oil fill tube and locking cap 5. hydraulic oil temperature sensor 6. implement return oil line 7. case drain return line (from case drain manifold) 8 main hydraulic oil line to suction manifold (for all hydraulic pumps) Not visible above is the pilot oil return line. It connects to the front side of the hydraulic tank, next to the hydraulic oil temperature sensor. A fluid level sight glass, which can be viewed from the right side of the machine, is located on the right side of the tank and is visible from the ground.
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9
7 10
6 11
5
4
2
3
1
105 The implement pump (1) for the D8T is a load sensing, pressure compensated, variable displacement piston pump. It is mounted to the upper, right rear corner of the flywheel housing. Mounted to the top of the implement pump is the main suction manifold (2), which supplies hydraulic oil to all of the hydraulic pumps in the hydraulic system. Additional components shown above are: 3. pressure compensator adjustment screw 4. flow compensator adjustment screw 5. signal line from the resolver network of the implement control valve stack 6. cold oil relief valve (not visible above, and on the opposite side of the manifold, is the line from the steering charge pump discharge to the cold oil relief valve) 7. main suction line connection to hydraulic tank 8. hydraulic demand fan pump supply line (suction) 9. steering charge pump supply line (suction) 10. implement pump case drain line 11. return oil line from the hydraulic oil cooler/fan motor
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Implement pump pressure settings are: - Low pressure standby for the implement hydraulic pump should be set to approximately 2860 ± 760 kPa (410 ± 110 psi). - Margin pressure for the implement pump should be set to approximately 2100 ± 172 kPa (305 ± 25 psi). - High pressure cutoff for the implement pump is approximately 24000 ± 520 kPa (3480 ± 75 psi). The main relief valve and the charging valve are installed in the inlet manifold. The main relief valve protects the system from pressure spikes over 27600 kPa (4000 psi). The charging valve restricts return flow to the tank that helps prevent cavitation in the cylinders.
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4
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6
2 7 9
1
8
10
106 The implement valve stack and pilot manifold are located in the notch of the fuel tank, under a protective cover (removed in the above illustration). The implement control valve stack assembly consists of two parallel valve sections (four if the machine is equipped with a ripper or a winch). At the left side of the assembly is the inlet manifold (1). The inlet manifold contains the pump discharge (HA) pressure test port (2) and the pump signal (HB) pressure test port (3). Either end of each implement control valve contains a control solenoid (9) and a pilot pressure test port (4) for testing pilot pressure at that end of the valve. The pilot manifold (7) is located at the right end of the assembly, bolted to the valve stack end cover (6). The pilot manifold contains the accumulator (5) and the pilot oil filter (8). The accumulator allows the operation of the implements for a short time when the engine is off. The pilot oil filter ensures that clean oil is sent to the solenoid controlled implement pilot valves. Implement pump supply oil enters the inlet manifold at the left end of the inlet manifold (not visible, above). Return oil from the implement control valves is directed back to the hydraulic oil tank from the outlet, through the hard tube (10) at the bottom of the manifold.
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5
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3 2
7 1
9
8
107 The illustration above shows the valve stack and pilot manifold assembly, as viewed from the front of the fuel tank. The charging valve (1) and the main relief valve (2) are contained in the inlet manifold. The charging valve (1) restricts the cylinder return oil flow to the tank. This valve keeps oil pressure in the cylinder return oil passage of the implement control valves and is used with the makeup valves to prevent cavitation in the cylinders. A typical function when the charging valve assists the makeup valve and the quick-drop valve for the lift cylinders is when the dozer control lever is moved to the full lower position (quick-drop) and the dozer is lowered rapidly. Opening pressure for the charging valve is approximately 1050 kPa (150 psi), at 190 ± 4 L/min (50 ± 1 gpm). The main relief valve (2) is set at approximately 27600 kPa (4000 psi), at 38 ± 4 L/min (10 ± 1 gpm). This setting is approximately 3585 kPa (520 psi) higher than the pressure compensator (cutoff) valve. The primary purpose of the main relief valve is to eliminate pressure spikes in the system. If the system is in a stall condition, the pressure cutoff valve will cause the implement pump to destroke toward a minimum angle.
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The implement control valves identified in illustration 106 are: 3. dozer lift valve 4. dozer tilt valve 5. ripper lift valve 6. ripper tip valve The pilot relief valve (7) is installed in the front side of the pilot manifold. Also visible in illustration 107 is the "float pilot boost" line (8) and the external resolver (9), which is the last resolver in the signal resolver network. The "float pilot boost" strategy will be discussed later in this presentation.
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2 3 1
4
5
6
108 The pilot manifold is mounted to the end cover (6) and is located at the right end of the valve stack. The implement lockout solenoid (1) is ENERGIZED when the implement lockout switch is in the UNLOCKED position, allowing pilot oil to flow to the control valves and enabling implement operation. When the lockout switch is in the LOCKED position, the solenoid is DE-ENERGIZED and pilot oil is prevented from flowing to the implement control valves. The implements will not move when the implement lockout switch is in the LOCKED position. The implement lockout solenoid (1) is also ENERGIZED when the engine is at low idle and the implement controls are in the HOLD position. Moving an implement control DE-ENERGIZES the implement lockout solenoid. The pressure reducing valve (2) lowers the pressure of the implement pump supply oil to pilot supply pressure, which is approximately 3275 kPa (475 psi). The implement pump pressure sensor (3) senses the implement pump supply pressure as it enters the pilot manifold. The hydraulic pilot supply (HPS) pressure test port (4) may be used to check pilot pressure. The hydraulic pilot accumulator pressure (HPAP) may be tested at the lower test port (5). Also located on the top of the pilot manifold (not visible above) are the accumulator check valve (at the left of the manifold) and the pilot filter bypass check valve (at the right of the manifold).
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D8T PILOT MANIFOLD From Solenoid Valve Drain Circuit
Screen
Implement Pump Pressure Sensor
To Implement Return
Implement Pump Supply
Pilot Supply
Pressure Reducing Valve Bypass Valve
Accumulator
Pilot Filter
Pilot Relief Valve
HPAP
Implement Lockout Valve
HPS
109 The pilot manifold is mounted to the end cover on the valve stack. It supplies pilot oil to the solenoid valves that are located on either end of each implement control valve. The pilot manifold is supplied with oil from the implement pump, through the inlet manifold, the valve stack, and then the end cover. The pilot manifold contains the implement pump pressure sensor, the pressure reducing valve, the Hydraulic Pilot Accumulator Pressure (HPAP) test port, and the Hydraulic Pilot Supply (HPS) pressure test port. As the oil enters the pilot manifold, it passes through a screen before it reaches the pressure reducing valve. The pressure reducing valve is infinitely variable, and meters the oil to provide pilot oil pressure of approximately 3275 ± 172 kPa (475 ± 25 psi). After passing through the pressure reducing valve, this oil becomes pilot oil. The pilot oil then passes through the pilot filter. From the pilot filter, the pilot oil then passes through the accumulator check valve, where it is available to the accumulator and the pilot relief valve.
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The pilot relief valve limits the pressure past the pressure reducing valve to approximately 6500 kPa (940 psi). In the event of pressure spikes in the pilot system, this valve opens to dissipate the excess pressure. The accumulator stores energy (pilot pressure) so that the implements may be lowered in a dead engine situation. A check valve is positioned upstream of the accumulator which prevents back-flow in the system in case of low pressure conditions. The check valve also prevents the accumulator from discharging when the machine is shut down. From the accumulator, the pilot oil then flows to the implement lockout valve. The implement lockout valve is solenoid operated and is ENERGIZED, when in the UNLOCKED condition. The implement lockout valve is controlled by the implement lockout switch, located on the right console, in the operator compartment. When this valve is in the LOCKED condition, or DE-ENERGIZED, the pilot oil is blocked and the implements cannot be moved with the implement controls. When the implement lockout valve is in the UNLOCKED condition, the pilot oil exits the pilot manifold at the outlet and is directed through a passage in the end cover and then through the pilot oil passages in the valve stack. Each implement valve then directs the pilot oil to the solenoid valves located on either end of each implement control valve. When the operator activates an implement, the appropriate solenoid valve directs the pilot oil into the pilot chamber of the valve. The pilot pressure then shifts the implement valve spool.
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110
6 2 7
111 5
3
4
The hydraulic oil cooler (1) is an oil-to-air type cooler. It is mounted vertically behind the AMOCS radiator, on the right side of the radiator guard. Return oil from the demand fan enters the cooler inlet (2) and is directed through the horizontal tube (3), toward the cooler outlet (4). When the oil is cold, the thermal bypass valve (5) remains open and the oil passes through the outlet and returns to the suction manifold. When the oil is warm, the bypass valve closes against the seat, forcing the oil upward through the cooling tubes (6) before returning to the outlet through the large vertical tube on the right side of the cooler (7). The cooled oil can then flow around the back side of the closed bypass valve to the outlet. Opening temperature for the thermal bypass valve is 62° - 65°C (143° - 149°F). When closed, the valve will open momentarily, in the event of pressure spikes in the system. Opening pressure for the bypass valve is 620 kPa (90 psi), at 71°C (159°F).
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D8T HYDRAULIC SYSTEM
Blade Lift Cylinder
SYSTEM HOLD
HB HA
Blade Tilt Cylinder
Quick-drop Valve Blade Lift
Dual Tilt Valve
HPDR HPDL
Blade Lift Cylinder
Float Boost Signal
Blade Tilt Cylinder
Blade Tilt
HPTL
Steering Control Valve
HD
HFPD
HPTR
Steering Motor
Steering Pump
Ripper Lift
Demand Fan Pump
HPRL
HPRR
Ripper Lift Cylinder
HC
Ripper Tip Cylinder
X1
X2
Ripper Tip
Fan Motor HPSO
Ripper Tip Cylinder
Steering Charge Filter
HPSI
Ripper Lift Cylinder Fluid Sampling
Cooler Bypass Valve
Hydraulic Oil Cooler
Pilot Manifold Implement Pump
Cold Oil Relief Valve
HPAP
Implement Lockout Valve
HPS
112 Implement System Operation This schematic shows the components and conditions in the implement system with the engine started and all the implements in HOLD. Oil is drawn from the hydraulic tank by the load sensing variable displacement, piston-type implement pump. Supply oil is directed to the closed-center control valves by the pump. Return oil from the control valves and pump case drain oil are sent to the tank. When a control lever is moved, oil from the implement control valve is directed to the double acting implement cylinders. The signal network line is in series with each control valve and passes through each valve body. The signal network terminates at the pump control valve. When an implement is activated, a signal is generated by the work port load. This signal is sent through the signal network. A resolver network inside the implement valves consists of a series of resolver valves which compare the signals from the implements and send the highest signal to the pump control valve. The major components in this system are: the implement pump, the inlet manifold, the blade lift and tilt control valves, the ripper lift and ripper tip control valves, the pressure reducing valve, the solenoid controlled pilot valves, the implement cylinders, and the quick-drop valve.
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D8T HYDRAULIC SYSTEM
Blade Lift Cylinder
BLADE RAISE
HB HA
Blade Tilt Cylinder
Quick-drop Valve Blade Lift
Dual Tilt Valve
HPDR HPDL
Blade Lift Cylinder
Float Boost Signal
Blade Tilt Cylinder
Blade Tilt
HPTL
Steering Control Valve
HD
HFPD
HPTR
Steering Motor
Steering Pump
Ripper Lift
Demand Fan Pump
HPRL
HPRR
Ripper Lift Cylinder
HC
Ripper Tip Cylinder
X1
X2
Ripper Tip
Fan Motor HPSO
Ripper Tip Cylinder
Steering Charge Filter
HPSI
Ripper Lift Cylinder Fluid Sampling
Cooler Bypass Valve
Pilot Manifold Implement Pump
Cold Oil Relief Valve
Hydraulic Oil Cooler
HPAP
Implement Lockout Valve
HPS
113 This schematic shows the components and conditions in the implement system with the engine started and the blade lift valve in the BLADE RAISE condition. When the operator moves the dozer control lever from HOLD to RAISE, the dozer control lever sends a signal to the Implement ECM. The Implement ECM then sends a corresponding current to the solenoid controlled blade lift pilot valve. The pilot valve opens to send pilot oil into the pilot chamber, which moves the main valve spool to the RAISE position. This allows high pressure pump supply oil to flow to the rod end of the blade lift cylinders and the blade raises. As the blade raises, oil from the head end of the lift cylinders returns through the blade lift control valve. It flows past the main valve spool and then back to the hydraulic tank. At the same time, the pressure in the rod end of the lift cylinders is felt in the blade lift control valve. That pressure, or load sensing signal, is transmitted through the signal resolver network back to the pump compensator valve. The pump compensator valve is set to command the pump to upstroke and increase pump flow to meet the demand.
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Text Reference
D8 T PRESSURE AND FLOW COMPENSATOR VALVE ENGINE OFF
Load Sensing Signal
Flow Compensat or Spool
Margin Spring
Adjustment Screw
Pressure Compensat or Spool
Orifice Pump Output
Case Drain Passage
Signal Passage to Large Actuator Piston
Cut off Spring
Adjustment Screw
114 Implement Pump Operation Shown here is the pressure compensator valve used on the implement pump. Two spools are installed in the valve: 1. The flow compensator (or margin) spool is the upper spool. This valve controls margin pressure and low pressure standby. Margin pressure is set at 2100 ± 172 kPa (305 ± 25 psi) above the signal pressure. Low pressure standby is set at 2825 ± 760 kPa (410 ± 110 psi). Adjusting the margin pressure to specification allows the standby pressure to be maintained within specification. 2. The pressure compensator (or cutoff) spool (on the right) controls the maximum pump pressure. The pressure compensator valve is set at 24000 ± 520 kPa (3480 ± 75 psi). NOTE: Each spring has an individual adjustment screw.
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Text Reference
D8T PUMP AND COMPENSATOR OPERATION ENGINE OFF Pump Output Cutoff Spring Margin Spring
Large Actuator Swashplate
Case Drain Passage
Load Sensing Signal
Drive Shaft Flow Compensator Spool Pressure Compensator Spool
Signal Passage to Actuator Piston
Small Actuator and Bias Spring Piston and Barrel Assembly
115 When the engine is OFF, the bias spring holds the swashplate at maximum angle. When the engine is started, the pump drive shaft starts to rotate. Oil is drawn into the piston bores. As the piston and barrel assembly rotates, the oil is forced out into the system.
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D8T PUMP AND COMPENSATOR OPERATION LOW PRESSURE STANDBY Pump Output Cutoff Spring Margin Spring
Large Actuator Swashplate
Case Drain Passage
Load Sensing Signal
Drive Shaft Flow Compensator Spool Pressure Compensator Spool
Signal Passage to Large Actuator
Small Actuator and Bias Spring Piston and Barrel Assembly
116 When no flow is demanded from the implements, no signal pressure is generated. System pressure (red and white stripes) generated by the pump is called "low pressure standby." The pump produces enough flow to compensate for system leakage at sufficient pressure to provide for instantaneous implement response when an implement is actuated. At machine start-up, the bias spring holds the swashplate at maximum angle. As the pump produces flow, system pressure begins to increase because the flow is blocked at the implement control valves. This pressure is felt under both the margin spool and the pressure cutoff spool. The margin spool moves up against the low spring force and permits system oil to go to the large actuator piston in the pump. As pressure in the large actuator piston increases, the large actuator piston overcomes the force of the bias spring and the pressure in the small actuator piston and moves the swashplate to a reduced angle. The large actuator piston moves to the right until the cross-drilled passage in the stem is uncovered. Oil in the large actuator piston then bleeds off to the pump case. At this minimum angle, the pump will produce just enough flow to make up for system leakage. The system pressure at this time is called "low pressure standby" and is approximately 2825 kPa (410 psi).
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Low pressure standby is higher than margin pressure. This characteristic is due to a higher back pressure created by the oil which is blocked at the closed-center valves when all the valves are in HOLD. Pump supply oil pushes the margin spool up and further compresses the margin spring. More supply oil then goes to the large actuator piston and flows through the crossdrilled hole in the stem to the pump case.
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Text Reference
D8T PUMP AND COMPENSATOR OPERATION UPSTROKING Pump Output Cutoff Spring Margin Spring
Large Reduced Actuator Pressure Swashplate
Case Drain Passage
Load Sensing Signal
Drive Shaft Flow Compensator Spool Pressure Compensator Spool
Signal Passage to Large Actuator
Small Actuator and Bias Spring Piston and Barrel Assembly
117 When an implement is moved and requires flow, a load sensing signal is sent to the pump compensator valve. This signal causes the force (margin spring plus signal pressure) at the top of the margin spool to become higher than the supply pressure at the bottom of the spool. The spool then moves down, blocks oil to the large actuator piston, and opens a passage to drain. Pressure at the large actuator piston is reduced or eliminated, which allows the bias spring to move the swashplate to an increased angle. The pump will now produce more flow. This condition is called "upstroking." The following conditions can result in upstroking the pump: 1. An implement control valve is activated when the system is at low pressure standby. 2. The control valve directional spool is moved for additional flow. 3. An additional circuit is activated. 4. Engine rpm decreases. In this case, pump speed decreases which causes a decrease in flow and pump supply pressure. The pump must then upstroke to maintain the system flow requirements.
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NOTE: Signal pressure does not necessarily need to increase for the pump to upstroke. For example, if one implement is activated and is operating at 13800 kPa (2000 psi), the system supply pressure is 15900 kPa (2305 psi) due to the maximum signal pressure of 13800 kPa (2000 psi) plus the margin spring force. If the operator activates another implement at an initial operating pressure of 6900 kPa (1000 psi), the maximum signal pressure is still 13800 kPa (2000 psi), but the supply pressure decreases momentarily to provide the increased flow now needed at the implements. The force at the top of the margin spool (now higher than the force at the bottom of the margin spool) pushes the spool down and allows oil in the pump control to drain. The swashplate angle increases and the pump provides more flow.
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Text Reference
D8T PUMP AND COMPENSATOR OPERATION CONSTANT FLOW Pump Output Cutoff Spring Margin Spring
Large Reduced Actuator Pressure Swashplate
Case Drain Passage
Load Sensing Signal
Drive Shaft Flow Compensator Spool Pressure Compensator Spool
Signal Passage to Large Actuator
Small Actuator and Bias Spring Piston and Barrel Assembly
118 As pump flow increases, pump supply pressure also increases. When the pump supply pressure (red) increases and equals the sum of the load pressure plus the force of the margin spring, the margin spool moves to a metering position and the system becomes stabilized. The difference between the signal pressure and the pump supply pressure is the value of the margin spring, which is approximately 2100 kPa (305 psi).
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Text Reference
D8T PUMP AND COMPENSATOR OPERATION DESTROKING Pump Output Cutoff Spring Margin Spring
Large Increased Actuator Pressure Swashplate
Case Drain Passage
Load Sensing Signal
Drive Shaft Flow Compensator Spool Pressure Compensator Spool
Signal Passage to Large Actuator
Small Actuator and Bias Spring Piston and Barrel Assembly
119 When less flow is needed, the pump is destroked. The pump destrokes when the pressure at the bottom of the margin spool becomes higher than combined signal pressure and spring force at the top. The margin spool then moves up and allows more flow to the large actuator piston. Pressure in the large actuator piston then overcomes the combined force of the small actuator piston and bias spring and moves the swashplate to a reduced angle. The pump will now produce less flow. The following conditions can result in destroking the pump: 1. All implement control valves are moved to the HOLD position. The pump returns to low pressure standby. 2. The control valve directional stem is moved to reduce flow. 3. An additional circuit is deactivated. 4. Engine rpm increases. In this case, pump speed increases causing an increase in flow. The pump destrokes to maintain system flow requirements. As pump flow decreases, pump supply pressure also decreases. When the pump supply pressure (red) decreases and becomes the sum of load pressure plus margin pressure, the margin spool moves to a metering position and the system stabilizes.
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NOTE: Signal pressure does not necessarily have to decrease for the pump to destroke. For example, if two implements are activated with one at 13800 kPa (2000 psi) and the other at 6900 kPa (1000 psi), the system supply pressure is 15900 kPa (2305 psi) due to the maximum signal pressure of 13800 kPa (2000 psi) plus the margin spring force. If the operator returns the implement at 6900 kPa (1000 psi) to HOLD, maximum signal pressure is still 13800 kPa (2000 psi), but the supply pressure increases due to reduced flow needed at the implements. The supply pressure will push the margin spring up and allow more oil to go to the pump control which causes the pump to destroke.
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Text Reference
D8T PUMP AND COMPENSATOR OPERATION HIGH PRESSURE STALL Pump Output Cutoff Spring Margin Spring
Large Increased Actuator Pressure Swashplate
Case Drain Passage
Load Sensing Signal
Drive Shaft Flow Compensator Spool Pressure Compensator Spool
Signal Passage to Large Actuator
Small Actuator and Bias Spring Piston and Barrel Assembly
120 The pressure compensator (or cutoff) spool is in parallel with the flow compensator (or margin) spool. The pressure compensator limits the maximum system pressure at any given pump displacement. The spool is held down during normal operation by the pressure compensator spring. During stall or when system pressure is at maximum, signal pressure is equal to pump supply pressure. The combination of the signal pressure and the margin spring forces the margin spool down. This movement of the margin spool normally opens a passage in the pump compensator valve for the oil in the large actuator piston to drain and causes the pump to upstroke. However, if the supply pressure is high enough, the pressure cutoff spool is forced up against the spring. This movement of the pressure cutoff spool blocks the oil in the large actuator piston from going to drain and allows supply oil to go to the large actuator piston. The increase in pressure allows the large actuator piston to overcome the combined force of the small actuator piston and bias spring to destroke the pump. The pump is now at minimum flow and pump supply pressure is at maximum. This condition is maintained for a single implement in a stall condition.
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This system also incorporates a main relief valve located in the inlet manifold. The pressure cutoff spool can be adjusted in the machine to destroke the pump at 24000 kPa (3480 psi). The main relief valve must be removed from the machine and adjusted to 27600 kPa (4000 psi), at 38 ± 4 L/min (10 ± 1 gpm) using the 1U5216 Test Block Manifold. This valve is set higher to limit pressure spikes in the system. When operating two or more implements with one in stall, the pump will produce flow to meet the needs of the other implements operating at a lower work port pressure. In this case, the pump could be producing up to maximum flow while the supply pressure is at the maximum of 24000 kPa (3480 psi). NOTE: Contained within the pump is a case drain relief valve. If the internal pressure exceeds 170 kPa (25 psi), excess flow will be directed to the inlet of the pump. The relief valve is designed to protect the pump shaft seals.
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Text Reference
D8T BLADE LIFT CONTROL VALVE BLADE HOLD
Main Spool
Rod End
Head End
Makeup Valve Signal Chamber
Cent ering Spring
Pilot Chamber
To Tank Pilot Supply
Float Pilot Boost Signal
From Blade Tilt Valve
Pilot Supply To Tank
Solenoid Valve
Flow Control Valve
Pump Supply Load Check Valve
To Pump Compensator Valve
121 Implement Control Valve Operation The blade lift control valve is the first valve in the stack. The blade lift control valve is a closed-center, electro-hydraulically operated valve controlled by pilot oil. The lift valve has four positions: RAISE, HOLD, LOWER, and FLOAT. Centering springs keeps the spool in the HOLD position when the blade lift cylinders are not in use. This visual shows the blade lift control valve in the HOLD condition. With the engine not running, the spring behind the flow control valve holds the flow control valve to the left. When the operator starts the machine, the pump sends oil through the inlet manifold to the flow control valve, through the throttling slots on the left side of the valve, through the load check valve to the main spool. With the main spool in the HOLD position, oil cannot flow to the cylinders, and oil pressure will begin to increase. The increasing pressure in the chamber to the right of the load check valve pushes the flow control valve to the right against the force of the spring. Moving the flow control valve to the right closes the throttling slot on the right side of the valve. Oil can continue to flow to the remaining control valves in the system. In HOLD, pressure at the main lift spool is equal to the flow control valve spring.
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Components of the implement control valves are: Flow control valve: Receives all the oil flow from the inlet manifold. The flow control valve provides the "pressure compensating" feature of the lift circuit by controlling the maximum pressure drop across the main spool. This operation results in a constant implement speed for a given lever displacement. If another implement in the system is activated, the pump will upstroke, providing more flow. The flow control valve will adjust to ensure that the increased flow does not affect the implement cylinder speed of this circuit. Load check valve: Prevents reverse implement flow when the operator moves a valve from HOLD and system pressure is lower than the cylinder or work pressure. Without the load check valve, the implement would drift down slightly (droop) before moving as commanded. The load check valve will open to allow supply oil to flow through the control valve when the system pressure is higher than the work port pressure. Resolver: Also called a double check valve. The resolver compares the signal between the valves and sends the highest resolved working pressure to the implement pump flow compensator. Although this visual shows the resolver and signal lines as external components, the resolver is inside the control valve and the signal lines are internally drilled passages. Main control spool: Controls oil flow to the implement and contains three cross-drilled holes that connect to an axial drilled passage in the center of the lift spool. The cross-drilled holes sense work port pressure in both the head and rod ends of the cylinders and transmit it to the pilot chamber. Makeup valve: Allows pressure in the tank to fill voids in the head end of the cylinders during times when cylinder supply pressure decreases below the tank pressure. Orifice: Provides smoother implement operation by delaying the rate that the signal pressure in the flow control spring cavity decreases when the operator changes implement directions. Solenoid controlled pilot valve: Is energized to allow pilot oil to pressurize the pilot chamber at the end of the main valve spool. The pilot oil shifts the main valve spool to allow pump supply oil to flow to the implement cylinders. When the solenoid valve is de-energized, the valve opens the pilot chamber to drain. This allows the main spool to move when shifted by the opposing solenoid valve, eliminating a hydraulic lock situation. NOTE: The throttling slot near the left end of the flow control valve is never completely closed and the check valve does not completely block oil from reaching the lift spool. A small amount of oil meters through the flow control valve and past the load check valve to maintain a pressure at the lift spool that is equal to the flow control valve spring force. Maintaining pressure at the main spool improves implement response. If the flow control valve is explained as a pressure reducing valve with a variable spring rate due to changes in signal pressure, the operation of the valve is easier to understand. The valve will limit the maximum pressure difference across the lift spool to the value of the flow control valve spring and cylinder pressure to provide constant flow for a given lever displacement.
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SOLENOID CONTROLLED PILOT VALVE OPERATION Solenoid De-Energized
Solenoid Energized
Pin Spring
Return to Tank
Return to Tank
Pilot Supply Pressure
Pilot Supply Pressure
From Chamber at End of Implement Control Valve Spool
To Chamber at End of Implement Control Valve Spool
Pilot Valve Spool
122 The proportional solenoid valves on either end of each implement control valve are energized to allow pilot supply oil to enter and pressurize the pilot chambers at the ends of the main control valve spools. When de-energized, the pilot chambers are open to tank. These valves are referred to as "pressure compensated proportional solenoid valves." The pilot supply pressure from the pressure reducing valve is approximately 3275 ± 172 kPa (475 ± 25 psi) as it enters the valve. When energized, the solenoid pushes a pin against the valve spool, forcing it down against the spring. This allows pilot oil to flow past the spool and enter the pilot chamber at the end of the implement control valve spool. The pressure in the pilot chamber also acts on the lower end of the pilot valve spool, forcing the spool up, against the solenoid pin. The result of these two forces is a reduced pilot pressure in the pilot chamber at the end of the control valve spool. The reduced pilot pressure may be tested at either end of each implement control valve using the pressure test ports installed at the factory. When in the fully energized state (approximately 1.4 amps), pilot chamber pressure should be approximately 2655 ± 70 kPa (385 ± 10 psi). The only exception to this rule is the LOWER/FLOAT end of the blade lift control valve. When the solenoid for blade lower/float is fully energized (approximately 1.9 amps), pilot chamber pressure should be approximately 2830 ± 70 kPa (410 ± 10 psi).
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D8T BLADE LIFT CONTROL VALVE BLADE RAISE
Rod End
Head End
Makeup Valve Signal Chamber Pilot Chamber
Hole
To Tank Pilot Supply
Float Pilot Boost Signal
From Blade Tilt Valve
Pilot Supply To Tank
Main Valve Spool
Solenoid Valve
Flow Control Valve
Pump Supply Load Check Valve
To Pump Compensator Valve
123 Shown above is a color cutaway of the blade lift control valve for the BLADE RAISE function. When the operator moves the dozer control lever from HOLD to RAISE, a signal is sent to the Implement ECM from the RAISE/LOWER position sensor on the dozer control lever. The Implement ECM then sends a corresponding current (approximately 1.4 amps for full raise) to energize the proportional blade raise solenoid valve. The solenoid valve then directs pilot oil to shift the main valve spool to the left, into the RAISE position. High pressure supply oil from the implement pump then flows past the flow control valve and the load check valve. The supply oil then flows past the main valve spool and out to the rod end of the lift cylinders and the blade raises. As the blade raises, oil from the head end of the lift cylinders returns through the head end passage of the blade lift control valve. The return oil then flows past the main valve spool and then into the passage to the hydraulic tank. At the same time, high pressure oil from the cylinder rod end passage of the implement control valve flows into the hole in the left end of the main valve spool. This is signal oil. This signal pressure is transmitted through the axial passage in the center of the valve spool and into the signal chamber, where it is directed to the the signal resolver passage. If this is the highest pressure in the signal resolver network, the signal resolver ball shifts to the right and the signal is sent to the pump compensator.
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The pump then UPSTROKES to meet the flow demand, in proportion to the signal pressure. If the compensator valve is properly adjusted, the pump will maintain a margin pressure of approximately 2100 ± 172 kPa (305 ± 25 psi) above the signal pressure. At the same time that the signal pressure is transmitted into the resolver network, the signal pressure is also sent to the spring chamber behind the flow control valve. This signal pressure, plus the force of the spring, keeps the flow control valve in a position to meter the pump supply oil. The flow control valve also maintains the proper flow of oil to the lift cylinders regardless of changes in load on the lift cylinders or increased flow from the pump due to the activation of another implement in the system. NOTE: The operation of the blade lift control valve for the BLADE LOWER function is similar to BLADE RAISE, except the opposite solenoid valve is ENERGIZED to allow pilot oil to shift the main valve spool to the LOWER position.
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Text Reference
D8T BLADE LIFT CONTROL VALVE BLADE FLOAT
Rod End
Head End
Makeup Valve Signal Chamber
Pilot Chamber
To Tank Pilot Supply Float Pilot Boost Signal
From Blade Tilt Valve
Pilot Supply To Tank
Solenoid Valve
Flow Control Valve
Pump Supply Load Check Valve
To Pump Compensator Valve
124 Shown above is a color cutaway of the blade lift control valve for the BLADE FLOAT function. When the operator moves the dozer control lever to the FLOAT position, a signal is sent to the Implement ECM from the blade raise/lower position sensor on the dozer control lever. The Implement ECM then sends a corresponding current (approximately 1.9 amps for FLOAT or LOWER) to energize the proportional blade lower solenoid valve. The solenoid valve then directs pilot oil to shift the main valve spool to the right, into the FLOAT position. In the FLOAT position, pump supply oil is blocked by the main valve spool. The rod end and head end passages to the lift cylinders are open to tank, allowing the cylinders to draw oil from the tank in either direction. The blade will follow the contour of the ground. The makeup valve may open momentarily if the blade lowers quickly, due to a sudden sudden change in the contour in the ground. To operate in the FLOAT condition, the operator must move the control lever all the way forward. When the control lever reaches the FLOAT detent, the FLOAT function is activated. The lever may be returned to the centered position and the FLOAT function will be maintained. To disable the FLOAT function, the lever must be moved either forward or rearward of the centered position.
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NOTE: The "float pilot boost" strategy is required to move the dozer control valve spool to the FLOAT position and maintain it. The "float pilot boost" strategy uses pilot oil to signal the pump to upstroke. This strategy causes the pump to maintain margin pressure above low pressure standby. The main control spool in the dozer lift control valve must move to its furthest position to attain the FLOAT function. This requires approximately 2825 kPa (410 psi) pilot pressure at the pilot chamber of the control valve. Normally, pilot pressure in the control valve chamber is approximately 2690 kPa (390 psi), which is somewhat less than what is needed. The low pilot pressure is caused by the lack of load sensing signal to the pump because the rod ends and the head ends of the dozer lift cylinders are open to tank, providing no load sensing signal when in FLOAT. When the pump receives no load sensing signal, the pump destrokes to low pressure standby. Low pressure standby is below pilot pressure, which is normally 3275 kPa (475 psi). When the pressure reducing manifold only receives standby pressure, it cannot produce a higher pilot pressure. The float pilot boost line directs the reduced pilot pressure from the control valve pilot chamber into the signal resolver network. The pump then senses the reduced pilot pressure as load sensing signal pressure and the pump upstrokes to maintain margin pressure above standby pressure. The pressure reducing manifold can now produce the normal pilot pressure and the necessary pilot pressure is then available to move the dozer control valve spool to the FLOAT position.
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Text Reference
D8T TILT CONTROL VALVE BLADE TILT RIGHT - SINGLE TILT
Rod End
Head End
To Tank Pilot Supply From Ripper Lift Valve Pilot Supply To Tank
Flow Control Valve
Pump Supply Load Check Valve
To Pump Compensator Valve
125 Shown above is a color cutaway of the blade tilt control valve for the TILT RIGHT function. When the operator moves the dozer control lever from HOLD to TILT RIGHT, a signal is sent to the Implement ECM from the blade tilt position sensor on the dozer control lever. The Implement ECM then sends a corresponding current (approximately 1.4 amps for full tilt right) to energize the proportional blade tilt right solenoid valve. The solenoid valve then directs pilot oil to shift the main valve spool to the right, into the TILT RIGHT position. High pressure supply oil from the implement pump then flows past the flow control valve and the load check valve. The supply oil then flows past the main valve spool and out to the rod end of the tilt cylinder and the blade tilts right (right side of the blade lowers). As the blade tilts, oil from the head end of the tilt cylinder returns through the head end passage of the control valve. The return oil flows past the main valve spool and then into the passage to the hydraulic tank. At the same time, high pressure oil from the cylinder rod end passage of the implement control valve flows into the hole in the left end of the main valve spool. This is signal oil. This signal pressure is transmitted through the axial passage in the center of the valve spool and into the signal chamber, where it is directed to the the signal resolver passage. If this is the highest pressure in the signal resolver network, the signal resolver ball shifts to the right and the signal is sent to the pump compensator.
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The pump then UPSTROKES to meet the flow demand, in proportion to the signal pressure. If the compensator valve is properly adjusted, the pump will maintain a margin pressure of approximately 2100 ± 172 kPa (305 ± 25 psi) above the signal pressure. At the same time that the signal pressure is transmitted into the resolver network, the signal pressure is also sent to the spring chamber behind the flow control valve. This signal pressure, plus the force of the spring, keeps the flow control valve in a position to meter the pump supply oil. The flow control valve also maintains the proper flow of oil to the lift cylinders regardless of changes in load on the lift cylinders or increased flow from the pump due to the activation of another implement in the system. The major difference in the blade tilt control valve from the other implement control valves in the system is that no makeup valves are included in either the rod end or the head end passages of the tilt circuit. Since the implement pump can supply the necessary volume of oil to fill the cylinder without cavitation, makeup valves are not necessary. NOTE: The operation of the blade tilt control valve for the TILT LEFT function is similar to TILT RIGHT, except the opposite solenoid valve is ENERGIZED to allow pilot oil to shift the main valve spool to the TILT LEFT position. On machines equipped with dual tilt, a second tilt cylinder is installed on the left side of the blade. A dual tilt valve is also installed between the tilt control valve and the two tilt cylinders. The rod end passage and the head end passage of the tilt control valve are reversed from that shown in illustration 124. Dual tilt valve operation will be discussed later in this presentation.
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Text Reference
D8T RIPPER LIFT CONTROL VALVE RIPPER RAISE Makeup Valve
Head End
Rod End
To Tank Pilot Supply From Ripper Tip Valve Pilot Supply To Tank
Flow Control Valve
Pump Supply Load Check Valve
To Pump Compensator Valve
126 Shown above is a color cutaway of the ripper lift control valve for the RIPPER RAISE function. When the operator pushes against the top of the ripper thumb switch, a signal is sent to the Implement ECM from the ripper raise/lower position sensor on ripper control handle. The Implement ECM then sends a corresponding current (approximately 1.4 amps for full raise) to energize the proportional ripper raise solenoid valve. The solenoid valve then directs pilot oil to shift the main valve spool to the right, into the RIPPER RAISE position. High pressure supply oil from the implement pump then flows past the flow control valve and the load check valve. The supply oil then flows past the main valve spool and out to the rod ends of the ripper lift cylinders and the ripper raises. As the ripper raises, oil from the head end of the ripper cylinders returns through the head end passage of the control valve. The return oil flows past the main valve spool and then into the passage to the hydraulic tank. At the same time, high pressure oil from the cylinder rod end passage of the implement control valve flows into the hole in the right end of the main valve spool. This is signal oil. This signal pressure is transmitted through the axial passage in the center of the valve spool and into the signal chamber, where it is directed to the the signal resolver passage. If this is the highest pressure in the signal resolver network, the signal resolver ball shifts to the right and the signal is sent to the pump compensator.
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Text Reference
The pump then UPSTROKES to meet the flow demand, in proportion to the signal pressure. If the compensator valve is properly adjusted, the pump will maintain a margin pressure of approximately 2100 ± 172 kPa (305 ± 25 psi) above the signal pressure. At the same time that the signal pressure is transmitted into the resolver network, the signal pressure is also sent to the spring chamber behind the flow control valve. This signal pressure, plus the force of the spring, keeps the flow control valve in a position to meter the pump supply oil. The flow control valve also maintains the proper flow of oil to the lift cylinders regardless of changes in load on the lift cylinders or increased flow from the pump due to the activation of another implement in the system. The RIPPER LOWER function is similar to the RIPPER RAISE function, except that the main valve spool is moved to the left. The valve spool then directs the pump supply oil to the head end of the ripper lift cylinders. The head end passage of the ripper control valve contains a makeup valve, which may open momentarily during RIPPER LOWER when the ripper is raised above the ground. When the ripper falls rapidly through the air, there is little signal to the implement pump due to the low work port pressure. The implement pump will destroke to standby pressure in this condition, so pump flow will be minimal. When the ripper drops faster than the implement pump can provide oil to fill the head end of the cylinders, the pressure in the head ends of the ripper cylinders becomes less than tank pressure. The makeup valves will open to supplement the reduced pump flow during this condition. As soon as any down pressure is sensed in the head end passage during RIPPER LOWER, the pump will upstroke to meet the demand and the makeup valve will close. NOTE: The operation of the ripper tip control valve is nearly identical to that of the ripper lift valve. The major difference between the two control valves is that the makeup valve is installed in the rod end passage of the ripper tip control valve.
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1 2
8
3 7 4
5
6
127 Dual Tilt Operation For machines equipped with dual tilt, the dual tilt valve (1) is mounted to the inside of the radiator guard, and just behind the left grill door. The dual tilt valve allows the operator to tilt the blade right or left to a greater degree than single tilt, pitch the blade forward (dump), and rack the blade back. Service points identified in the above illustration are: 2. high pressure line from tilt control valve (head end) 3. pilot oil drain line (to case drain) 4. pilot supply line from the steering charge pump 5. dual tilt solenoid 6. high pressure line from tilt control valve (rod end) 7. tilt line connections to the left tilt cylinder 8. tilt line connections to the right tilt cylinder
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D8T DUAL TILT VALVE DUAL TILT RIGHT
Left Tilt Cylinder
From Tilt Control Valve
Right Tilt Cylinder
To Tilt Control Valve
To Rod End
To Head End
Pilot Supply From Steering Charge Pump
Tilt Coil From Trigger Switch Pitch Coil From Thumb Switch
128 The dual tilt valve has three modes of operation. They are: - DUAL TILT - SINGLE TILT - BLADE PITCH Charge pressure oil from the steering charge pump is used as pilot oil for moving the dual tilt valve spool. The pilot oil is controlled by a dual action solenoid valve. The dual action solenoid valve has two coils - a "tilt coil" and a "pitch coil." When the thumb switch on the dozer control lever is moved to the right or the to left, the pitch solenoid coil is ENERGIZED and the solenoid valve directs pilot oil to the bottom of the dual tilt valve spool, moving the spool up. The blade will then PITCH FORWARD or RACK BACK, depending on which direction the switch is moved. When the trigger switch on the dozer control lever is depressed, the tilt solenoid coil is energized (when the default tilt mode is set to DUAL TILT) and the solenoid valve directs pilot oil to the top of the dual tilt valve spool, moving the spool down. If the default tilt mode is set to SINGLE TILT, the tilt solenoid coil is always ENERGIZED. The trigger switch will then toggle to the DUAL TILT mode when the switch is depressed and the tilt coil is then DE-ENERGIZED. (The default tilt mode can be set using Cat Advisor.)
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Illustration 128 shows the dual tilt valve in the DUAL TILT RIGHT condition. This is the default mode of operation unless the operator has set the default tilt mode to single tilt, using Cat Advisor. In the dual tilt mode the tilt solenoid coil is always DE-ENERGIZED and the dual tilt spool remains centered by the centering springs on either end of the spool. When the operator moves the dozer control lever to the right, commanding the TILT RIGHT function, pump supply oil from the head end passage of the blade tilt control valve flows out to the head end of the left tilt cylinder. The left tilt cylinder rod extends and forces the left tilt cylinder rod end oil out to the dual tilt valve. The left cylinder rod end oil flows around the dual tilt spool and out to the rod end of the right tilt cylinder. The right tilt cylinder rod retracts. The right tilt cylinder head end oil is then forced out, back to the dual tilt valve where it flows around the dual tilt spool and returns to the rod end passage of the blade tilt control valve as return oil. When the left tilt cylinder rod extends and the right tilt cylinder rod retracts, the blade tilts right. For DUAL TILT LEFT, the flow of oil through the tilt circuit is reversed. In the DUAL TILT LEFT condition, the left tilt cylinder rod retracts and the right tilt cylinder rod extends. NOTE: For information about how to set the default tilt mode for the dual tilt valve, see the Service Training presentation SERV1790, "Caterpillar Monitoring and Display System with Advisor for Track-type Tractors."
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D8T DUAL TILT VALVE SINGLE TILT RIGHT
Left Tilt Cylinder
From Tilt Control Valve
Right Tilt Cylinder
To Tilt Control Valve
To Rod End
To Head End
Pilot Supply From Steering Charge Pump
Tilt Coil From Trigger Switch Pitch Coil From Thumb Switch
129 Illustration 129 shows the dual tilt valve in the SINGLE TILT RIGHT condition. If dual tilt has been selected as the default tilt mode, the operator must depress and hold the trigger switch to toggle to SINGLE TILT mode. This results in the tilt solenoid coil being ENERGIZED and the solenoid valve directs pilot oil to the top of the dual tilt spool, moving the spool down. When the operator moves the dozer control lever to the right, commanding a TILT RIGHT function in the SINGLE TILT mode, pump supply oil from the head end passage of the blade tilt control valve flows out to the head end of the left tilt cylinder. The left tilt cylinder rod extends and forces the rod end oil out to the dual tilt valve. The left cylinder rod end oil flows around the dual tilt spool. With the spool shifted down, the passages to the right tilt cylinder are blocked, but the passage back to the blade tilt control valve are open. The left tilt cylinder rod end oil then flows back through the rod end passage of the blade tilt control valve and then back to tank. When the left tilt cylinder rod extends and the right tilt cylinder remains stationary, the blade TILTS RIGHT, but the angle of the tilt is not as acute as when in dual tilt mode. For SINGLE TILT LEFT, the flow of oil through the tilt circuit is reversed. In the SINGLE TILT LEFT condition, the left tilt cylinder rod retracts and the right tilt cylinder remains stationary.
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D8T DUAL TILT VALVE BLADE PITCH FORWARD
Left Tilt Cylinder
From Tilt Control Valve
Right Tilt Cylinder
To Tilt Control Valve
To Rod End
To Head End
Pilot Supply From Steering Charge Pump
Tilt Coil From Trigger Switch Pitch Coil From Thumb Switch
130 Illustration 130 shows the dual tilt valve in the PITCH FORWARD condition. To pitch the blade forward, the operator must move the thumb rocker switch on the dozer control lever to the right (away from the operator). This results in the pitch solenoid coil being ENERGIZED. The solenoid valve then directs pilot oil to the bottom of the dual tilt spool, moving it up. When the operator has commanded a PITCH FORWARD function, pump supply oil from the head end passage of the blade tilt control valve flows out to the head end of the left tilt cylinder. The left tilt cylinder rod extends and forces the left tilt cylinder rod end oil out to the dual tilt valve. The left cylinder rod end oil flows around the dual tilt spool. With the spool shifted up, the oil flows through the passage to the head end of the right tilt cylinder. The right tilt cylinder rod extends also, forcing the right tilt cylinder rod end oil back to the dual tilt valve. The right tilt cylinder rod end oil then flows back through the blade tilt control valve, then back to tank. Since the volume of rod end oil in the left tilt cylinder is less than the capacity of the head end of the right tilt cylinder, the left cylinder rod will fully extend before the right tilt cylinder head is filled with oil. When the left tilt cylinder reaches its full extension, the bypass valve will open and oil will continue to flow to the head end of the right tilt cylinder. This results in the left cylinder reaching its full extension slightly before the right cylinder.
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When the left and the right tilt cylinder rods extend, the blade will PITCH FORWARD. To RACK BACK the blade, the operator must move the thumb rocker switch on the dozer control lever to the left (toward the operator). The flow of oil through the tilt circuit is reversed. In the RACK BACK condition, both the left and the right tilt cylinder rods retract. When the left and the right tilt cylinder rods retract, the blade will RACK BACK. NOTE: Machines equipped with dual tilt are also equipped with the Auto Blade Assist (ABA) feature. Blade positions for ABA are LOAD, CARRY, and SPREAD (or DUMP). All three of these functions automatically activate the dual tilt valve and the tilt control valve and will PITCH FORWARD or RACK BACK the blade to preset positions. These positions can be adjusted using Cat Advisor. Briefly, these three blade positions are defined as: - LOAD position is when the dozer blade is pitched slightly forward for an aggressive cutting edge angle to LOAD the blade. - CARRY position is when the dozer blade is racked back in a fully retracted, nonaggressive cutting edge angle so that the blade tends to CARRY material. - SPREAD position is when the dozer blade is pitched fully forward to quickly and cleanly empty the dozer blade and SPREAD the material. The blade may be raised and lowered manually during these automatic cycles without interrupting the cycles. NOTE: When the thumb rocker switch on the dozer control lever is moved to the PITCH FORWARD position, the TILT RIGHT solenoid controlled pilot valve on the blade lift control valve is ENERGIZED to send pump supply oil to the dual tilt valve. When the thumb rocker switch on the dozer control lever is moved to the RACK BACK position, the TILT LEFT solenoid controlled pilot valve on the blade lift control valve is ENERGIZED to send pump supply oil to the dual tilt valve.
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QUICK-DROP VALVE
To Rod End To Implement Control Valve
Dozer Lift Cylinders To Head End Quick-drop Valve
131 Quick-drop Valve Shown in the illustration above is a schematic of the single quick-drop valve. The valve is mounted on top of the engine hood at the front of the machine. In the schematic, components in the quick-drop valve are shown with the blade on the ground. The variable orifice sleeve is the essential component in the valve and functions to create the pressure necessary to move the valve spool and direct rod end oil to the head end in the QUICK-DROP mode.
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QUICK-DROP VALVE HOLD
To Left Cylinder Head End
To Right Cylinder Head End
To Left Cylinder Rod End
To Right Cylinder Rod End Passage to Plunger End
Plunger
Valve Spool
Cover Cover Orifice Sleeve
To/From Lift Control Valve
Passage to Spool End
132 Shown in this illustration are the components of the single quick-drop valve: the orifice sleeve, the plunger, the valve spool, the right and left covers, and the spring. As shown in the previous illustration, the valve components are shown with the dozer blade on the ground. Both the orifice sleeve and the plunger can float in the valve and their positions in HOLD depend on the previous action of the lift control valve: RAISE, LOWER or FLOAT.
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QUICK-DROP VALVE DOZER RAISE
From Right Cylinder Head End
From Left Cylinder Head End
To Right Cylinder Rod End
To Left Cylinder Rod End
Passage to Plunger End Plunger
Valve Spool
Cover Cover Orifice Sleeve
To/From Lift Control Valve
Passage to Spool End
133 When the lift spool in the blade lift control valve is moved to the RAISE position, supply oil enters the quick-drop valve through the passage on the left and moves the orifice sleeve to the right. The oil then flows out to the rod end of the lift cylinders. Return oil from the head end of the lift cylinders enters the quick-drop valve and flows past the valve spool to the blade lift control valve. Return oil pressure then enters the passage to the plunger end inside the valve spool and is felt on the right end of the plunger. However, the blade RAISE pressure felt on the left end of the plunger is higher than the return oil pressure and keeps the plunger shifted to the right. Blade RAISE pressure also enters the passage to the right end of the spool. Since the same pressure is felt on the left end of the spool, the spring keeps the spool shifted to the right. NOTE: The orifice sleeve floats on the valve spool and is kept on the spool by a retaining ring.
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QUICK-DROP VALVE DOZER LOWER
To Right Cylinder Head End
To Left Cylinder Head End
From Right Cylinder Rod End
From Left Cylinder Rod End
Passage to Plunger End Plunger Valve Spool
Cover Cover Orifice Sleeve
To/From Lift Control Valve
Passage to Spool End
134 As the operator moves the dozer control lever forward to LOWER the blade (but not to within 3° - 4° of the "soft" FLOAT detent), return oil from the rod end of the lift cylinders enters the quick-drop valve. The return oil flows past the orifice sleeve to the control valve and moves the orifice sleeve to the left against the retaining ring. This oil flow creates a pressure differential across the orifice sleeve. Supply oil (red striped) from the blade lift control valve enters the quick-drop valve and flows past the valve spool to the head end of the lift cylinders. Supply oil pressure enters the passage to the plunger end and is felt on the right end of the plunger. However, the return oil pressure (red/white hatch) on the left end of the plunger is higher and keeps the spool shifted to the right. Rod end return oil pressure (red and white hatch) enters the passage to the right end of the spool. This pressure is also felt on the major diameter at the left end of the spool just to the right of the orifice sleeve. In addition, return oil pressure, after the pressure drop across the orifice sleeve, is felt on the minor diameter at the left end of the spool. The net result is that the spool and plunger are kept to the right because of the spring and return pressure. The major diameters of the spool (the effective area at the right end and the effective area just to the right of the orifice sleeve) cancel each other. The pressure on the right end of the spool is not high enough to overcome the spring and return oil pressure on the minor diameter at the left end on the spool.
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QUICK-DROP VALVE QUICK-DROP
To Right Cylinder Head End
To Left Cylinder Head End
From Right Cylinder Rod End
From Left Cylinder Rod End
Passage to Plunger End Plunger Valve Spool
Cover Cover Orifice Sleeve
To/From Lift Control Valve
Passage to Spool End
135 When the dozer blade is rapidly lowered to the ground, the blade control lever has been moved to a forward position that is within 3° - 4° of the "soft" FLOAT detent, and the quick-drop valve operates in the QUICK-DROP mode. The increased lever travel results in higher cylinder rod end flow and a higher pressure drop across the orifice sleeve. The only difference from the dozer LOWER position is that the pressure drop across the orifice sleeve that is felt on the minor diameter of the right end of the spool overcomes the resistance of the spring, and the spool starts to move. The minimum flow that causes the necessary pressure drop across the orifice sleeve to begin spool movement is referred to as the "trigger point" and occurs at a point just before the float detent of maximum lever travel. When the spool starts to move, the effective area of the orifice sleeve decreases and the pressure drop increases to shift the spool even farther. The result is that the spool shifts completely to the left. This movement connects the rod end of the lift cylinders to the head end of the lift cylinders across the slots in the spool. This connection provides even less resistance and the downward blade velocity and flow from the rod ends increase. This connection also provides a "filling" function to minimize the pause time. Some of the oil from the rod ends still flows across the orifice sleeve causing a pressure drop to keep the spool shifted.
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QUICK-DROP VALVE DOZER LOWER WITH DOWN PRESSURE To Right Cylinder Head End
To Left Cylinder Head End
From Left Cylinder Rod End
From Right Cylinder Rod End Passage to Plunger End
Plunger
Valve Spool
Cover Cover Orifice Sleeve
To/From Lift Control Valve
Passage to Spool End
136 When the blade contacts the ground and stops, flow from the rod end of the lift cylinders stops. With no pressure drop across the orifice, the spring shifts the spool to the right. After the pump fills the head end of the cylinders (pause time) and the head end cylinder pressure starts to increase, the blade begins to move down. Supply oil pressure (red and white stripes) enters the passage to the right end of the plunger. Return oil pressure (red and white hatch) from the rod end of the lift cylinders is felt on the left end of the plunger. This pressure is lower than the oil pressure (red and white stripes) on the right end of the plunger, and the plunger moves to the left. The pressure drop across the orifice sleeve that is felt on the minor diameter of the right end of the spool works to move the spool to the left. However, this movement is resisted by the spring and the supply oil pressure (red and white stripes) acting on the plunger. Therefore, the spool stays shifted to the right.
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137 The quick-drop valve (arrow) is mounted on top of the radiator guard, under a protective hinged cover. The cover has a locking tab due to the radiator fill tube and cap being located under the cover, also.
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1
2
138 AutoCarry Components For machines equipped with AutoCarry, there are three major components included in the implement system, not including software and wiring harnesses. These components are: - dozer lift cylinder position sensor (right lift cylinder only) - dynamic inclination sensor - ground speed radar The illustration above shows the lift cylinder position sensor (1) installed on the top of the right dozer lift cylinder. This sensor provides a feedback signal to the Implement ECM. The Implement ECM uses this information to determine how much the lift cylinder piston moves when cylinder movement is automatically commanded by the Implement ECM, during the CARRY segment of the AutoCarry cycle. The wiring harness for the position sensor is attached at the connector (2).
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139 For machines equipped with AutoCarry, a dynamic inclination sensor (arrow) is installed on the front of the main case, just above the drive shaft. The dynamic inclination sensor determines the angle of incline and side slope on which the machine is operating, then transmits that data to the Implement ECM. This data is used as one of the factors to determine auto blade positioning during the CARRY segment of the AutoCarry cycle.
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140 The third major component present on machines with AutoCarry is the Ground Speed Radar (arrow). This component is mounted to a bracket that is attached to the saddle. It senses actual ground speed through an opening in the bottom guard. The ground speed signal is sent to the Implement ECM. Ground speed is compared to the target speed. Target speed is determined by considering the torque converter output speed sensor, the angle of inclination on which the machine is operating, and the Load Factor setting (which is an "offset" setting that the operator can adjust using Cat Advisor). All of this information is used by the Implement ECM (which contains the AutoCarry software) to make automatic adjustments to blade height during the CARRY segment of the AutoCarry cycle.
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CATERPILLAR MONITORING AND DISPLAY SYSTEM COMPONENTS D8 T TRACK-TYPE TRACTOR + Implement ECM
J2
J1
Power Train ECM
Key St art Swit ch J2
J1
Engine ECM
J2
J1
(
)
Navigat or / CTCT CAN A At t achment s Dat a Link Product Link
CAN A Dat a Link CAT Dat a Link 15
20
AUTO
25
10
5
AUTO
X1 0 0
n/ min
0
Dynamic Inclination Sensor
CAN B Dat a Link
Advisor
CAN C Dat a Link
30
35
2 .3
1F
1 3 2 .1
Inst rument Clust er
Comm Adapt er II
Fuel Level Sender Rear Act ion Lamp
Act ion Alarm
ET
Alt ernat or ( R-Terminal)
141 ELECTRICAL SYSTEM The illustration above shows a graphical representation of the The Caterpillar Monitoring and Display System. The hardware components in the system include Cat Advisor, the instrument cluster, the Engine ECM, the Implement ECM, the Power Train ECM, the Action Alarm, the rear Action Lamp, and various switches, sensors and senders. The illustrations on the following pages show the engine, the power train, and the implement electrical systems. They also identify all of the switches, sensors, senders, and solenoids that are the input and the output devices used in each system. Depending on how the machine is equipped, some or all of these devices may be present. Also shown in these illustrations is the means by which these components and systems communicate with each other and how the information from the input and output devices is shared between systems. Communication of information on standard machines occurs through the following data links: - Cat Data Link - CAN A Data Link (high speed) - CAN C Data Link (high speed) With AutoCarry or other automated earthmoving attachments, the D8T will also include a CAN B Data Link (shown in dashed lines, above) and a CAN D Data Link (not shown).
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D8T ENGINE ELECTRICAL SYSTEM COMPONENTS C15 ACERT ENGINE
Implement ECM
CAN A Data Link CAT Data Link
Hydraulic Oil Temperature Sensor
J2
J1
Pre-lube Relay
J2 J1 Engine ECM CAN A Data Link
CAT Data Link
Secondary Fuel Filter Bypass Switch
Key Start Switch
Coolant Flow Switch
Intake Air Pressure Sensor
Advisor
Injector No.1 Injector No.2
Coolant Temp. Sensor
Injector No.3
Fuel Pressure Sensor
Injector No.4
Intake Manifold Temp. Sensor Engine Oil Pressure Sensor
Injector No.5 High/Low Idle Switch Decelerator Position Sensor
Injector No.6 Fuel Temp. Sensor
Cam Speed/Timing Sensor Turbo Inlet Pressure Sensor
Crank Speed/Timing Sensor
Demand Fan Pump Pressure Sensor
Crank W/O Inject Plug
Atmospheric Pressure Sensor Timing Calibration Connector Reversing Fan Switch (Attachment)
Fan Pump Control Solenoid Ether Aid Solenoid Fan Bypass Solenoid (Attachment) Fan Reversing Valve Solenoid (Attachment) OUTPUT COMPONENTS
INPUT COMPONENTS
142 Shown above is an illustration of the electrical system for the C15 ACERT engine used in the D8T Track-type Tractor. The hydraulic demand fan considers the engine coolant temperature, the intake manifold air temperature, and the hydraulic oil temperature as inputs for controlling the fan. Since the hydraulic demand fan is controlled by the Engine ECM, hydraulic oil temperature data from the Implement ECM is shared with the Engine ECM through the high speed CAN A Data Link. To view the status of all the engine components shown above using Cat Advisor: - select the Service option from the Home Menu to display the Service Menu - select System Status from the Service Menu to display the System Status Menu - select Engine from the System Status Menu - use the ARROW buttons to page through the list of components Cat ET may also be used to view the status of these components.
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D8T POWER TRAIN ELECTRICAL SYSTEM
Engine ECM
J2 J1
Power Train ECM
J2 J1
CAN A Data Link CAT Data Link
CAT Data Link
Key Start Switch Trans. Charge Filter Bypass Switch
Service Brake Position Sensor
Transmission Output Speed Sensor No.1
Secondary Brake Switch
Transmission Output Speed Sensor No.2
Torque Conv. Charge Filter Bypass Switch
AutoShift Switch
Torque Converter Output Speed Sensor
Steering Charge Filter Bypass Switch
Auto Kickdown Switch
Steering Motor Speed/Direction Sensor
Torque Converter Oil Temp. Sensor Trans. Oil Temp. Sensor (Sump)
(3) Steering Lever Position Sensors
Forward Switch
Trans. Lube Oil Temp. Sensor (D9T Only)
F-N-R Position Sensor
Reverse Switch
Steering Pump Charge Pressure Sensor
Transmission Reverse Clutch (Solenoid No. 1) Transmission Forward Clutch (Solenoid No. 2) Transmission Third Gear Clutch (Solenoid No. 3) Transmission Second Gear Clutch (Solenoid No. 4) Transmission First Gear Clutch (Solenoid No. 5) Left EH Steering Pump Solenoid Valve Right EH Steering Pump Solenoid Valve Service Brake Solenoid Valve Secondary Brake Solenoid Valve
Parking Brake Switch Steering Control Lever
Primary (Crank) Engine Speed/Timing Sensor
Advisor
Upshift Switch
Parking Brake Solenoid Valve
Downshift Switch
Priority Valve Solenoid Backup Alarm
Harness Code Plug /Location Code OUTPUT COMPONENTS
INPUT COMPONENTS
143 Shown above is an illustration of the electrical system for the D8T Track-type Tractor power train. The Power Train ECM determines engine lug and torque curves by comparing engine speed data to the torque converter output speed data. The Power Train ECM uses this information to determine when to automatically downshift the transmission for the Auto KickDown feature. Since the D8T does not have an engine output speed sensor, as did previous D8R machines, the primary (crankshaft) speed/timing sensor provides engine speed data to the Engine ECM, which shares that data with the Power Train ECM through the CAN A Data Link. To view the status of all the power train components shown above using Cat Advisor: - select the Service option from the Home Menu to display the Service Menu - select System Status from the Service Menu to display the System Status Menu - select Ptrain from the System Status Menu - use the ARROW buttons to page through the list of components Cat ET may also be used to view the status of these components.
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D8T IMPLEMENT HYDRAULICS ELECTRICAL SYSTEM
Power Train ECM
J2 J1
Implement Hydraulics ECM CAT Data Link
CAT Data Link
Advisor
CAN A Data Link
CAN A Data Link
Blade Raise/Lower Position Sensor (Forward/Rearward)
Key Start Switch Implement Lockout Switch
Blade Tilt Position Sensor (Left/Right) Blade Control Lever Torque Converter Output Speed Sensor
J2 J1
Blade Mode Select Switch (Left Push-Button)
Blade Manual Select Switch (Right Push-Button) Dual/Single Tilt Toggle Trigger Switch Blade Pitch/Angle Position Sensor (Thumb Switch)
Auto Blade Assist Switch (Attachment) Auto Carry Switch (Attachment) Dynamic Inclination Sensor (Attachment)
Implement Pump Pressure Sensor
Blade Tilt Right Solenoid
Hydraulic Oil Temp. Sensor
Blade Tilt Left Solenoid
Harness Code Plug Location Code Ground Speed Radar (Attachment) Lift Cylinder Position Sensor (Attachment)
Ripper Raise/Lower Position Sensor (Control Lever)
Blade Lower Solenoid
Dual/Single Tilt Solenoid (Attachment)
Shank In Solenoid
Dual Tilt Pitch Solenoid (Attachment)
Shank Out Solenoid
Ripper Auto Stow Switch
Ripper Tip In/Out Position Sensor (Control Lever)
Blade Raise Solenoid
Ripper Control Handle
Quick-Drop Solenoid (D9T Only) Implement Shutoff Solenoid
Ripper Raise Solenoid
Ripper Lower Solenoid
OUTPUT COMPONENTS
INPUT COMPONENTS
144 Shown above is an illustration of the electrical system for the D8T Track-type Tractor implement system. The Implement ECM requires torque converter output speed data to determine track speed, if the machine is equipped with AutoCarry. Track speed is determined by a calculation using torque converter output speed sensor data. The Power Train ECM monitors this sensor and shares this information with the Implement ECM through the CAN A Data Link. To view the status of all the implement system components shown above using Cat Advisor: - select the Service option from the Home Menu to display the Service Menu - select System Status from the Service Menu to display the System Status Menu - select Implement from the System Status Menu - use the ARROW buttons to page through the list of components Cat ET may also be used to view the status of these components.
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145
CONCLUSION This presentation has discussed components locations and system operations of the engine, the cooling system, the power train, the implement hydraulics, the electrical system, and the Caterpillar Monitoring and Display System (Advisor). When used in conjunction with the Service Manual and the STMG 790, "Caterpillar Monitoring and Display System with Advisor for Track-type Tractors," the information in this package will help the serviceman analyze problems in any of the major systems of this tractor.
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HYDRAULIC SCHEMATIC COLOR CODE Black - Mechanical Connection. Seal
Red - High Pressure Oil
Dark Gray - Cutaway Section
Red / White Stripes - 1st Pressure Reduction
Light Gray - Surface Color
Red Crosshatch - 2nd Reduction in Pressure
White - Atmosphere Or Air (No Pressure)
Pink - 3rd Reduction in Pressure
Purple - Pneumatic Pressure
Red / Pink Stripes - Secondary Source Oil Pressure
Yellow - Moving or Activated Components
Orange* - Pilot, Signal or Torque Converter Oil
Cat Yellow - (Restricted Usage) Identification of Components within a Moving Group
Orange / White Stripes** Reduced Pilot, Signal or TC Oil Pressure
Brown - Lubricating Oil
Orange / Crosshatch - 2nd Reduction in Pilot, Signal or TC Oil Pressure
Green - Tank, Sump, o r Return Oil
Blue - Trapped Oil
Green / White Stripes Scavenge / Suction Oil or Hydraulic Void
*
Also used as steering / charge oil in this presentation
**
Also used as reduced steering / charge oil in this presentation
HYDRAULIC SCHEMATIC COLOR CODE This illustration identifies the meanings of the colors used in the hydraulic schematics and cross-sectional views shown throughout this presentation.
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1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41.
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VISUAL LIST Title slide 42. Engine oil/power train oil coolers Operator compartment 43. Turbo inlet air pressure sensor Seat 44. Fuel system schematic Steering control lever (tiller) 45. Engine air flow components Right console 46. Cooling system schematic Dozer control lever 47. Radiator guard rear view Ripper control handle 48. Radiator guard rear/bottom view Machine function switches 49. Radiator guard front view Fuse panel and Cat ET comm port 50. Hydraulic fan drive system schematic - max HVAC and wiper/washer controls 51. Hydraulic fan drive system schematic - min Dash 52. Fan pump cutaway - maximum fan speed Brake pedal and decelerator pedal 53. Fan pump cutaway - minimum fan speed Power Train and Implement ECMs 54. Reversing fan system hydraulic schematic Monitoring system components view 55. Fan pump components ID Monitoring system components ID 56. Fan motor and reversing valve Instrument cluster ID 57. Fan reversing valve components ID Advisor panel 58. Power train components ID Advisor panel ID 59. Power train electronic control system Advisor Start-Up screen 60. Power train hydraulic schematic Advisor warning screen 61. Power train major components location Advisor Performance 1 of 2 screen 62. Power train oil pump Advisor Performance 2 of 2 screen 63. Power train filters, priority valve location C15 ACERT engine title slide 64. Priority valve operation - normal mode Left side engine view 65. Priority valve operation - priority mode Right side engine view 66. Torque divider Fuel filters 67. Torque divider cutaway Secondary fuel filter components ID 68. Torque converter inlet/lube distribution Fuel transfer pump and components ID 69. Torque converter inlet relief valve operation Engine pre-lube pump/motor 70. Torque converter outlet relief valve Atmospheric and engine oil pressure sensors 71. Torque converter outlet relief valve operation Engine ECM 72. Power train oil cooler Engine turning tool and TDC ports 73. Power shift transmission - disassembled Intake air temperature sensor 74. Transmission modulating valve operation Crank-Without-Inject plug 75. Transmission main relief valve operation Engine oil filter, fill tube, dipstick, S•O•S 76. Power shift transmission cutaway Intake manifold air (boost) pressure sensor 77. Electronic brake control valve Secondary (cam) speed/timing sensor 78. Electronic brake control valve cutaway Coolant temperature sensor 79. Brake control valve operation - released Coolant flow switch/water pump 80. Brake control valve operation - engaged Turbo/alternator/AC compressor 81. Brake control valve operation - park engaged Turbocharger/wastegate/oil line 82. Power train oil fill tube and dipstick
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Text Reference
VISUAL LIST 83. Power train remote pressure taps 124. Blade lift control valve (blade float) 84. Transmission clutch pressure taps 125. Blade tilt control valve (tilt right-single tilt) 85. Trans. lube/main relief/brake pressure taps 126. Ripper lift control valve (ripper raise) 86. Brake lube/brake pressure taps (final drive) 127. Dual tilt valve component ID 87. Brake pedal and position sensor 128. Dual tilt valve cutaway (dual tilt right) 88. Quick-Change oil couplings 129. Dual tilt valve cutaway (single tilt right) 89. Final drive/brake/differential cutaway 130. Dual tilt valve cutaway (blade pitch 90. Differential steer system schem. - no steer forward) 91. Differential steer system components ID 131. Quick-drop valve circuit (schematic) 92. Steering lever position sensors 132. Quick-drop valve cutaway (hold) 93. Steering charge filter location and ID 133. Quick-drop valve cutaway (dozer raise) 94. Steering motor 134. Quick-drop valve cutaway (dozer lower) 95. Steering motor speed/direction sensor 135. Quick-drop valve cutaway (quick-drop) 96. Steering motor cutaway - flushing valve 136. Quick-drop valve cutaway (down pressure) 97. Steering pump components ID (#1) 137. Quick-drop valve location/ID 98. Steering pump components ID (#2) 138. Lift cylinder position sensor 99. Steering pump operation - side cutaway 139. Dynamic inclination sensor 100.Steering pump operation - ends cutaway 140. Ground speed radar camera 101.Steering pump operation - top cutaway 141. Monitoring system/electrical schematic 102.Differential steer system schem. - left steer 142. Engine electrical components 103.Implement hydraulic system block diagram 143. Power train electrical components 104. Hydraulic tank 144. Implement hydraulics electrical components 105. Implement pump 145. D8T rear view - conclusion 106. Valve stack (rear view) 107. Valve stack (front view) 108. Pilot manifold - component ID 109. Pilot manifold schematic 110. Hydraulic oil cooler 111. Hydraulic oil cooler bypass valve 112. Implement system schematic-System Hold 113. Implement system schematic-Blade Raise 114. Implement Pump compensator operation 115. Impl. Pump operation (engine off) 116. Impl. Pump operation (low press. standby) 117. Impl. Pump operation (upstroking) 118. Impl. Pump operation (constant flow) 119. Impl. Pump operation (destroking) 120. Impl. Pump operation (high pressure stall) 121. Blade lift control valve (blade hold) 122. Solenoid pilot valve operation 123. Blade lift control valve (blade raise)
STMG 789 10/04
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Serviceman's Handout No. 1
Engine System Components Identification Directions: Use this sheet to take notes during the presentation. During the lab exercise, use this sheet as a checklist when locating and identifying the components. Engine Components ____ Primary and Secondary fuel filters
____ Ether injection control
____ Electric fuel priming pump and switch
____ Intake air pressure sensor
____ Fuel transfer pump
____ Atmospheric pressure sensor
____ Engine oil fill tube and dipstick
____ Intake air temperature sensor
____ Engine oil filter
____ Fuel temperature sensor
____ Engine oil S•O•S test port
____ Fuel pressure sensor
____ Engine oil pressure test port
____ Fuel filter bypass sensors
____ Engine oil pressure sensor
____ Engine oil pressure sensor
____ Engine pre-lube motor and pump
____ Turbo inlet pressure sensor
____ Engine oil cooler
____ "Crank-without-Inject" connector/plug
____ Air filter
____ Crankshaft timing sensor
____ Turbocharger
____ Camshaft timing sensor
____ AMOCS radiator and shunt tank
____ Starter
____ Engine coolant S•O•S test port
____ Coolant temperature sensor
____ Water pump
____ Coolant flow switch
____ Temperature regulator housing
____ Timing calibration probe connector
____ Main electrical disconnects
____ Block heater element
____ A4 Engine ECM
____ Block heater AC power receptacle
____ Alternator
____ Auxiliary start receptacle
STMG 789 10/04
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Serviceman's Handout No. 2
Cooling System and Demand Fan System Components Identification Directions: Use this sheet to take notes during the presentation. During a lab exercise, use this sheet as a checklist when locating and identifying the components. Cooling System Components
Demand Fan System Components
____ Engine oil cooler
____ Hydraulic demand fan pump
____ Power train oil cooler
____ Fan pump control valve
____ Jacket water pump
____ Fan pump pressure control solenoid
____ AMOCS radiator cores
____ Fan pump discharge pressure sensor
____ Water temperature regulator housing
____ Hydraulic Fan Pump Discharge pressure test port (HDFP)
____ Coolant shunt tank ____ Fan motor ____ Coolant fill tube and cap ____ Fan reversing valve ____ Coolant level sight glass ____ Manual fan reversing switch ____ Radiator drain valve ____ Engine coolant temperature sensor ____ ATAAC core ____ Intake manifold temperature sensor ____ Hydraulic oil temperature sensor ____ A4 Engine ECM
STMG 789 10/04
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Serviceman's Handout No. 3
Power Train Components Identification Directions: Use this sheet to take notes during the presentation. During a lab exercise, use this sheet as a checklist when locating and identifying the components. Power Train Components
Power Train Pressure Test Ports
____ Power Train ECM
____ Torque converter outlet relief pressure test port (N)
____ Power train oil pump ____ Flywheel lube pressure (L2) ____ Power train oil fill tube and dipstick ____ Transmission lube pressure (L1) ____ Power train lube distribution manifold ____ Torque converter inlet relief valve ____ Torque converter outlet relief valve ____ Torque converter outlet temp. sensor ____ Power train oil cooler ____ Transmission charging filter ____ Torque converter charging filter ____ Priority valve and solenoid
____ Torque converter inlet relief pressure test port (M) ____ Transmission main relief pressure test port (P) ____ Priority valve pressure test port (PV) ____ Transmission clutch pressure test ports ____ Transmission filter outlet pressure test port ____ Torque converter charging filter inlet pressure test port
____ Power train oil temperature sensor (sump) ____ Torque converter charging filter outlet pressure test port ____ Power train filter bypass switches ____ Torque converter output speed sensor ____ Electronic brake control valve ____ Service brake pedal sensor ____ Parking brake switch
____ Power train oil S•O•S port ____ Right brake lube pressure test port (LB2) ____ Right brake pressure test port ____ Left brake lube pressure test port (LB1) ____ Left brake pressure test port ____ Brake pressure test port (B)
STMG 789 10/04
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Serviceman's Handout No. 4
Hydraulic System Components Identification Directions: Use this sheet to take notes during the presentation. During a lab exercise, use this sheet as a checklist when locating and identifying the components. Implement Hydraulic Components
Implement Hydraulic Pressure Test Ports
____ Hydraulic oil tank
____ Implement pump discharge pressure test port (HA)
____ Hydraulic oil fill tube and sight glass ____ Pump signal pressure test port (HB) ____ Case drain hydraulic oil filter ____ Accumulator pressure test port (HPAP) ____ Implement pump and compensator valve ____ Pilot supply pressure test port (HPS) ____ Pilot manifold ____ Pilot pressure test ports (8 ports, at control ____ Implement pump discharge pressure sensor valves) ____ Implement lockout solenoid valve ____ Pilot filter ____ Valve stack, including end cover and inlet manifold ____ Charging valve ____ Main relief valve ____ Implement control valve solenoid valves ____ Main pump suction manifold ____ Quick-drop valve ____ Dual tilt valve ____ Fan reversing valve (if equipped) ____ Implement ECM ____ Hydraulic oil cooler and bypass valve ____ Hydraulic oil temperature sensor
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Serviceman's Handout No. 5
Steering System Components Identification Directions: Use this sheet to take notes during the presentation. During a lab exercise, use this sheet as a checklist when locating and identifying the components. Steering System Components
Steering System Pressure Test Ports
____ Hydraulic oil tank
____ Right steer pump actuator piston pressure test port (X1)
____ Hydraulic oil fill tube and sight glass ____ Case drain filter ____ Steering pump ____ Steering charge pump ____ Pump control solenoid "A" (steer right) ____ Pump control solenoid "B" (steer left) ____ Steering charge filter ____ Steering charge filter bypass switch ____ Steering charge pressure sensor ____ Cold oil relief valve ____ Steering motor ____ Steering motor speed/direction sensor ____ Steering control lever ____ Steering lever position sensors ____ Power Train ECM
____ Left steer pump actuator piston pressure test port (X2) ____ Steering charge pump discharge pressure test port (F) ____ Left steering loop pressure test port (HC) ____ Right steering loop pressure test port (HD)
Clutch 1 REV
Clutch 2 FWD
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Fill in the blanks with the names of the components or the service points.
Clutch 5 1st
Clutch 3 3rd
Clutch 4 2nd
FIRST GEAR FORWARD
D8T POWER TRAIN SCHEMATIC
STMG 789 10/04 Serviceman's Handout No. 6
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Fill in the blanks with the names of the components.
D8T IMPLEMENT HYDRAULIC SYSTEM
STMG 789 10/04 Serviceman's Handout No. 7
TOP VIEW
Fill in the blanks with the names of the components.
LEFT TURN
D8T STEERING PUMP
SIDE VIEW
STMG 789 10/04 - 184 Serviceman's Handout No. 8
ENGINE OFF Fill in the blanks with the names of the components.
D8T PUMP AND COMPENSATOR OPERATION
STMG 789 10/04 - 185 Serviceman's Handout No. 9
Fill in the blanks with the names of the components.
Head End
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Pump Supply
Rod End
BLADE HOLD
D8T BLADE LIFT CONTROL VALVE
STMG 789 10/04 Serviceman's Handout No. 10
