824H Wheel Dozer, 825H Soil Compactor and 826H Landfill Compactor Braking System Caterpillar

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Escaping fluid under pressure, even a pinhole size leak, can penetrate body tissue, causing 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 possible causes to problems. Since there may be several possible causes, specific inspections or instrument tests may be recommended. These inspections and tests will help to identify the causes that are most probable.

This section covers possible causes of brake problems for the 824H Wheel Dozer, the 825H Soil Compactor, and the 826H Landfill Compactor.

The 824H Wheel Dozer is equipped with service brakes at all four wheels. The 825H Soil Compactor and the 826H Landfill Compactor are equipped with service brakes at the front wheels. Some of the examples may not be applicable to all of the models.

Note: Use oil with the correct viscosity for the operating conditions.

• POSSIBLE PROBLEM LIST FOR THE SERVICE BRAKES

1. The accumulator pressure will not reach cutout pressure at low idle. This may cause a Warning Category 3 to occur. This may also engage the parking brake.

2. The front service brakes do not operate, and the warning system is not activated.

3. The rear service brakes do not operate, and the warning system is not activated.

4. The service brakes slip, and the warning system is not activated.

5. Too much force needed to push the brake pedals, and the warning system is not activated.

• Possible Causes of Problems with the Service Brakes

Problem 1

The accumulator pressure does not reach the cutout pressure at low idle. This typically causes a Warning Category 3 to occur. The oil pressure light for the brakes will flash. The action lamp will flash, and the action alarm will sound. This problem may also engage the parking brake.

Possible cause

1. When the hydraulic oil is hot and the engine is running at low idle, the output of a bad pump is not sufficient to overcome the pump's own internal losses.

2. The combination valve is not functioning properly.

Problem 2

The front service brakes do not operate, and the warning system is not activated.

Possible causes

1. The brake group within the axle housing is damaged.

2. The lines to the front service brakes are obstructed.

3. The service brake control valve is not diverting oil to the front brake circuit.

4. The combination valve is not supplying oil pressure to the accumulator for the front service brake circuit.

Problem 3

The rear service brakes do not operate, and the warning system is not activated.

Possible causes

1. The brake group within the axle housing is damaged.

2. The lines to the rear service brakes are obstructed.

3. The service brake control valve is not diverting oil to the rear brake circuit.

4. The combination valve is not supplying oil pressure to the accumulator for the rear service brake circuit.

Problem 4

The service brakes slip, and the warning system is not activated.

Possible causes

1. One or both axles contain an incorrect hydraulic oil additive.

2. The brake discs in the axle housing are worn.

3. The lines to one or both axles could be obstructed.

4. The hydraulic system is contaminated. This can cause the control valves to malfunction.

5. The service brake control valve is faulty.

Problem 5

Too much force is needed to push the brake pedal, and the warning system is not activated.

Possible causes

1. The brake pedals and/or brake pedal linkages are damaged.

2. The brake valve is sticking because of contaminated oil.

• POSSIBLE PROBLEM LIST FOR THE PARKING BRAKE

1. The parking brake does not hold the machine stationary.

2. The parking brake does not engage when the parking brake control knob is pulled out and the alert indicator is NOT flashing.

3. The parking brake does not engage when the parking brake control knob is pulled out and the alert indicator IS flashing.

4. The parking brake will not disengage.

• Possible Causes of Parking Brake Problems

Problem 1

The parking brake does not hold the machine stationary.

Possible causes

1. The brake shoes are badly worn.

2. The parking brake needs to be adjusted.

3. The linkage for the parking brake actuator is not adjusted properly or the actuator linkage is adjusted for the manual disengagement of the parking brake.

4. There is grease or oil on the brake components.

Problem 2

The parking brake does not engage when the parking brake control knob is pulled out and the alert indicator is not flashing.

Possible causes

1. The parking brake cable is disconnected.

2. The parking brake cable has stretched until the cable will not actuate the parking brake.

3. The parking brake control valve is not functioning properly.

Problem 3

The parking brake does not engage when the parking brake control knob is pulled out and the alert indicator IS flashing.

Possible Cause

1. The components in the parking brake are damaged or the brake needs adjustment.

2. The linkage for the parking brake actuator is adjusted for manual disengagement of the brake.

Problem 4

The parking brake will not disengage.

Possible Causes

1. The control cable could be disconnected or the cable may need adjustment.

2. If the alert indicator for the parking brake is flashing, there is a problem with the parking brake control valve.

3. If the service brakes for the front axle are not working properly, there is a problem with the oil pressure in the front brake circuit.

• POSSIBLE PROBLEM LIST FOR THE SERVICE BRAKE CHARGING SYSTEM

1. The low oil pressure warning will not turn off.

• Possible Causes of problem in the Service Brake Charging System

Problem 1

The low oil pressure warning will not turn off.

Possible causes

1. There is inadequate pump pressure for the brake system.

   Note: If you can turn off the warning by increasing the rpm of the engine, the cause of the problem is the brake pump.

2. If the service brakes are NOT functioning properly, and the parking brake is NOT disengaging properly, the accumulator charging valve is not functioning properly.

3. If the service brakes are functioning properly and the parking brake is disengaging properly, the oil pressure switch is bad.

4. The hydraulic oil is too hot.