924K, 930K and 938K Wheel Loaders Electrohydraulic System Caterpillar

Refer to the following procedure before you perform any tests or any adjustments of the power train. For all tests, the power train oil must be at normal operating temperature.

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Sudden movement of the machine or release of oil under pressure can cause injury to persons on or near the machine. To prevent possible injury, perform the procedure that follows before testing and adjusting the power train.

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Personal injury can result from hydraulic oil pressure and hot oil. Hydraulic oil pressure can remain in the hydraulic system after the engine has been stopped. Serious injury can be caused if this pressure is not released before any service is done on the hydraulic system. Make sure all of the attachments have been lowered, oil is cool before removing any components or lines. Remove the oil filler cap only when the engine is stopped, and the filler cap is cool enough to touch with your bare hand.

Note: Permit only one operator on the machine. Keep all other personnel away from the machine or in the sight of the operator.

If the required hydraulic oil temperature is difficult to maintain during Testing and Adjusting, the following methods for warming the oil may be performed.

First, a stall, and flow procedure may be performed. One implement function should be stalled and another function moved through the full range of movement no more than ten cycles.

1. Ensure that the bucket/work tool is free of debris so that the dump/rack back function may be performed safely.

2. Stall the auxiliary hydraulic function or the raise function.

   Note: If a work tool is attached, disconnecting the auxiliary hydraulic lines may be necessary in order to stall the auxiliary function.

3. While stalling the above function, operate the dump/rack back function for ten cycles.

4. Release the auxiliary function or joystick to the center position terminating the stall condition.

5. Flow oil by operating the raise/lower or dump/rack back function for several cycles without another function stalled.

6. Repeat Steps 2 through 5 as necessary to warm the hydraulic oil.

Illustration 1	g02997678
The 938 hydraulic oil cooler shown at the rear of the machine. The hydraulic oil cooler is located between the arrows.

The second method of warming the hydraulic oil is performed by placing an air restriction over the hydraulic oil cooler. The hydraulic oil cooler is shown in Illustration 1. The air restriction should only be in place long enough to increase the hydraulic oil temperature to the required specification. Remove the air restriction over the hydraulic oil cooler when the hydraulic oil temperature is within test specifications.

1. Move the machine to a smooth, horizontal location that is away from operating machines and away from personnel.

2. Place the transmission direction in the NEUTRAL position.

3. Engage the parking brake. Place wheel blocks in front of the wheels and behind the wheels.

4. Lower the bucket or the work tools to the ground.

5. Stop the engine.

6. Install the steering frame lock.

7. With the engine keyswitch in the ON position "engine stopped" move the control levers through the full range of travel. Moving the controls in this manner will relieve any pressure that may be present in the implement hydraulic system.

8. Depress the brake pedal repeatedly. Depressing the brake pedal repeatedly will relieve any pressure that may be present in the brake hydraulic system.

Troubleshooting can be complex, but many problems can be identified by performing a visual inspection first.

If the visual checks are completed but the problem has not been identified, perform operational checks.

Reference: For the proper procedure, refer to the Testing and Adjusting manual.

Remember that a problem is not necessarily caused by one part, but by the relation of one part with other parts. Service personnel must find the problem and the source of the problem before the necessary repairs can be completed.