904B Wheel Loader Hydraulic and Steering System Caterpillar

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Personal injury or death can result from machine articulation or movement. Machine frames can move and a person can be crushed. Connect the steering frame lock link between the front and rear frames before working on machine.

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Personal injury or death can result from escaping fluid under pressure. Escaping fluid under pressure, even a very small pin-hole size leak, can penetrate body tissue and cause serious injury and possible death. If fluid is injected into your skin, it must be treated immediately by a doctor familiar with this type of injury. Always use a board or cardboard when checking for a leak.

This section provides probable causes to known problems. Perform a visual inspection of the machine. Refer to Testing and Adjusting, "Visual Inspection". Prepare the machine for troubleshooting. Refer to Testing and Adjusting, "Machine Preparation for Troubleshooting".

Operational Checks

Operate the machine in each direction and in all speeds. Note the noises that are not normal and find the sources of the noises. If the machine is not operating correctly, refer to "Troubleshooting Problem List".

Steering Turns

Measuring the steering turns will determine if there is a reason to check the steering priority valve or the hand metering unit.

Illustration 1	g01145037
Steering frame lock in the UNLOCKED position

Note: The following test will be performed with the steering frame lock in the UNLOCKED position.

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

2. Place the machine in the NEUTRAL position.

3. Disengage the parking brake.

4. Raise the attachment slightly off the ground.

5. Run the engine at HIGH idle.

6. Articulate the machine from the full LEFT position to the full RIGHT position. Record the number of turns of the steering wheel from stop to stop.

7. Articulate the machine from the full RIGHT position to the full LEFT position. Record the number of turns of the steering wheel from stop to stop.

8. If the recorded number of turns is higher than the number of turns in Table 1, refer to "Troubleshooting Problem List".
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   Table 1

   STEERING TURNS
   Stop to Stop	Revolutions
   LEFT to RIGHT	3.0 ± 0.5
   RIGHT to LEFT	4.2 ± 0.5

Troubleshooting Problem List

1. Turning the steering wheel is difficult.

2. The machine does not turn evenly.

3. The machine does not turn when the steering wheel is turned.

4. The pump makes noise and the steering cylinder rod does not move freely.

Troubleshooting Probable Causes

Problem 1

Turning the steering wheel is difficult.

Probable causes

1. The oil is cold.

2. The oil is contaminated.

3. There is a restriction in an oil line of the steering metering pump.

4. The implement and steering pump pressure is low.

5. There is a leak or blockage in the load sensing line.

Problem 2

The machine does not turn evenly.

Probable causes

1. The oil is contaminated.

2. The metering pump is sticking.

3. The priority valve spool is sticking.

4. The steering cylinder is scored.

Problem 3

The machine does not turn when the steering wheel is turned.

Probable causes

1. The metering pump is faulty.

2. The priority valve spool is sticking.

3. There is a mechanical failure in the steering linkage.

4. The piston seals and/or the steering cylinder is worn.

Problem 4

The pump makes noise and the steering cylinder rod does not move freely.

Probable causes

1. There is air in the hydraulic circuit.

2. The pump has too much wear.

3. There is a loose connection of the oil line on the inlet side of the hydraulic pump.

4. The viscosity of the oil is incorrect.

5. The oil level in the hydraulic oil tank is low.