854K Wheel Dozer Hydraulic System Caterpillar

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The drive shaft rotates between the torque converter and the transmission whenever the engine is running. Contact with the rotating shaft can result in personal injury or death. The rotating shaft is located under the implement and steering pumps. Do not allow personnel into the pump bay area behind the cab when the engine is running.

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Sudden movement or accidental starting of the machine can cause personal injury or death to persons on or near the machine. To prevent personal injury or death, perform the following: Park the machine on a smooth, level surface. Lower the work tool to the ground and engage the parking brake. Stop the engine and remove the key. Block the wheels and install the steering frame lock.

The hydraulic fan pump is a variable displacement piston pump that is pressure compensated and flow compensated. The pump control valve controls cutoff pressure of the piston pump. Also, the pump control valve controls the margin pressure of the piston pump. The margin pressure is the difference between the output pressure of the pump and the signal pressure of the pump. The solenoid valve (demand fan) varies the control signal to the pump. The control signal changes the pump output.

Measure the margin pressure with the pump swashplate midway between the MAXIMUM OUTPUT position and the MINIMUM OUTPUT position. The Caterpillar Electronic Technician (ET) software must be used in order to override the solenoid valve (demand fan). Caterpillar ET will then provide the correct control pressure to the pump control. The solenoid valve (demand fan) is controlled by the engine ECM.

Note: Caterpillar ET is a software program that can be used on an IBM compatible personal computer.

ReferenceTo use Caterpillar ET, order Special Publication, JERD2124, "ET Single Use Program License", Special Publication, JEHP1026, "Information and Requirements Sheet", and Special Publication, JERD2142, "Data Subscription". The Special Publication, JEHP1026, "Information and Requirements Sheet" lists the required hardware and the features of Caterpillar ET.

Illustration 1	g01493353
Location of Components of Hydraulic Fan Drive (1) Pressure tap for signal pressure. (2) Pump control valve. (3) Hydraulic fan pump. (4) Solenoid valve (demand fan). (5) Adjustment for cutoff pressure (upper screw). (6) Upper locknut. (7) Pressure tap for discharge pressure.

The components of the hydraulic fan system are located in the back of the pump compartment.

1. Attach an unvalved nipple to a 0 to 25000 kPa (0 to 3600 psi) pressure gauge. Attach a hose from 1U-5482 Pressure Adapter Group to the unvalved nipple. Attach the hydraulic line to pressure tap (7) on the diagnostic plate.

2. Attach an unvalved nipple to a 0 to 25000 kPa (0 to 3600 psi) pressure gauge. Attach a section of hydraulic line to the unvalved nipple. Attach the hydraulic line to pressure tap (1) on the solenoid valve (demand fan) (4) .

3. Engage the parking brake.

4. Shift the transmission to neutral.

5. Start the engine. Warm the hydraulic oil to normal operating temperature of approximately 49 to 65°C (120 to 150°F).

6. Connect Caterpillar ET to the data link connector. The data link connector is next to the keypad. Start Caterpillar ET.

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Illustration 2	g01483653

7. Select "854K". Select "Diagnostics and Diagnostic tests". Select "Override Parameters and Engine Fan Bypass".

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Illustration 3	g01483693

8. Enter "54%" for the "Engine Fan Bypass Override Parameter". This should provide a control pressure of 4650 to 9050 kPa (675 to 1310 psi) at high idle. Change the setting for the "Engine Fan Bypass Override Parameter" in order to obtain the correct pressure range if the "54%" setting does not provide the correct pressure range.

9. With the engine at high idle, observe both gauge readings.

10. The margin pressure of hydraulic fan pump (3) is the difference between the output pressure of the pump and the control pressure of the pump. This difference should be 2100 ± 100 kPa (305 ± 15 psi).

11. If the cutoff pressure of the hydraulic fan pump is not correct, the pressure compensator must be adjusted.

12. Stop the engine.

13. Loosen locknut (6) .

14. Turn adjustment screw (5) clockwise in order to increase the pressure setting. Turn adjustment screw (5) counterclockwise in order to decrease the pressure setting.

15. Tighten locking nut (6) .

Perform this entire procedure again in order to verify the new setting.