993K Wheel Loader Electrohydraulic 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.

Illustration 1	g01446683
Pressure taps in pump compartment (1) Pressure tap for fan pump discharge

Illustration 2	g01446701
Left side of pump compartment (2) Pressure tap for signal pressure (3) Hydraulic fan pump

Illustration 3	g01446706
Hydraulic fan pump for standard ambient temperature cooling (view from drive end) Location of adjustment screw for margin pressure

Illustration 4	g01446717
Hydraulic fan pump for high ambient temperature cooling Location of adjustment screw for margin pressure

1. Attach 8T-0860 Pressure Gauge to the pressure tap for fan pump discharge (1). Refer to Illustration 1.

2. Attach 8T-0860 Pressure Gauge to the pressure tap for signal pressure (2). Refer to Illustration 2.

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 on the control panel on the right side of the cab. Start Caterpillar ET.
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   Illustration 5	g01446423

7. Select "C32 993K". Select "Diagnostics". Select "Diagnostic Tests". Select "Override Parameters".
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   Illustration 6	g01446718

8. Select "Engine Fan Bypass". Change the value for this parameter to "54%". This should provide a control pressure of 7500 to 14600 kPa (1100 to 2100 psi) for machines with standard ambient temperature cooling at high idle. The control pressure for machines with high ambient temperature cooling at high idle should be 8050 to 15700 kPa (1175 to 2300 psi). Change the setting for the "Engine Fan Bypass" 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 (300 ± 15 psi).

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

    If the margin pressure is correct, proceed to Step 17.

12. Stop the engine.

13. Loosen the locknut for the adjustment screw for margin pressure.

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

15. Tighten the locknut.

16. Perform Step 5 through Step 10 of the test procedure again in order to verify the new setting for the margin pressure.

17. Use Caterpillar ET in order to reset the "Engine Fan Bypass" parameter.

18. Exit the Caterpillar ET program and disconnect ET from the machine.