770G and 772G Off-Highway Truck (OEM) Hydraulic and Braking System: Brake System Troubleshooting

Performance Checks For Brake System

NOTICE
Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting, and repair of the product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids. Refer to Special Publication, NENG2500, "Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Cat products.Dispose of all fluids according to local regulations and mandates.

Do not check for leaks with your hands. Pin hole (very small) leaks can result in a high velocity oil stream that will be invisible close to the hose. This oil can penetrate the skin and cause personal injury. Use cardboard or paper to locate pin hole leaks.

Problem: The service brakes do not engage correctly.

Probable Cause

• Mud or dirt under the pedal does not allow the service brake foot pedal valve to engage fully.
• There is no oil pressure from the brake charging pump.
• The Brake Valve (Front Service Brake) is damaged or malfunctioning.
• The Brake Valve (Rear Service Brake, Retarder Control, Traction Control) is damaged or malfunctioning.
• The Control Manifold (Brake Accumulator Charge) is set incorrectly or the Control Manifold (Brake Accumulator Charge) is damaged.
• There is wear or damage to the double check valve.
• There is wear or damage to the hydraulic cylinders.
• There is wear or damage to the slack adjusters.
• There is air in the oil for the brake hydraulic system.
• A brake piston seal leakage exists.
• There is wear or damage to the brakes.

Problem: The service brakes do not release correctly.

Probable Cause

• Mud or dirt under the pedal does not allow the service brake foot pedal valve to release fully.
• The Brake Valve (Front Service Brake) is damaged or malfunctioning.
• The Brake Valve (Rear Service Brake, Retarder Control, Traction Control) is damaged or malfunctioning.
• There is wear or damage to the hydraulic cylinders.
• There is wear or damage to the one-way check valves.
• There is wear or damage to the slack adjusters.
• There is air in the oil for the brake hydraulic system.
• There is wear or damage to the brakes.
• There are broken brake release springs.

Problem: The secondary brakes do not engage correctly.

Probable Cause

• There is wear or damage to the Brake Valve (Parking) or the Brake Valve (Parking) is malfunctioning.
• The Control Manifold (Brake Accumulator Charge) is set incorrectly or the Control Manifold (Brake Accumulator Charge) is damaged.
• There is wear or damage to the traction control valve or the traction control valve is malfunctioning.
• The Brake ECM is malfunctioning.
• There is wear or damage to the hydraulic cylinders.
• There is wear or damage to the secondary brake pedal position sensor.
• There is air in the oil for the brake hydraulic system.
• A brake piston seal leakage exists.
• There is wear or damage to the parking brakes.

Problem: The secondary brakes do not release correctly.

Probable Cause

• There is no oil pressure from the brake charging pump.
• There is wear or damage to the Brake Valve (Parking) or the Brake Valve (Parking) is malfunctioning.
• The Brake ECM is malfunctioning.
• There is wear or damage to the hydraulic cylinders.
• There is wear or damage to the secondary brake pedal position sensor.
• There is air in the oil for the brake hydraulic system.
• There is wear or damage to the parking brakes.
• There are broken brake release springs.

Problem: The parking brakes do not engage correctly.

Probable Cause

• There is wear or damage to the Brake Valve (Parking) or the Brake Valve (Parking) is malfunctioning.
• The Brake ECM is malfunctioning.
• There is wear or damage to the parking brakes.
• There are broken brake springs.

Problem: The parking brakes do not release correctly.

Probable Cause

• There is no oil pressure from the brake charging pump.
• There is wear or damage to the Brake Valve (Parking) or the Brake Valve (Parking) is malfunctioning.
• The Brake ECM is malfunctioning.
• There is wear or damage to the hydraulic cylinders.
• There is wear or damage to the one-way check valves.
• A brake piston seal leakage exists.
• There is wear or damage to the parking brakes.

Problem: The retarder does not engage correctly.

Probable Cause

• The Brake Valve (Front Service Brake) is damaged or malfunctioning.
• The Brake Valve (Rear Service Brake, Retarder Control, Traction Control) is damaged or malfunctioning.
• There is no oil pressure from the brake charging pump.
• The Control Manifold (Brake Accumulator Charge) is set incorrectly or the Control Manifold (Brake Accumulator Charge) is damaged.
• The Brake ECM is malfunctioning.
• There is wear or damage to the double check valve.
• There is wear or damage to the hydraulic cylinders.
• There is wear or damage to the slack adjusters.
• There is air in the oil for the brake hydraulic system.
• A brake piston seal leakage exists.
• There is wear or damage to the brakes.

Problem: The retarder does not release correctly.

Probable Cause

• The Brake Valve (Front Service Brake) is damaged or malfunctioning.
• The Brake Valve (Rear Service Brake, Retarder Control, Traction Control) is damaged or malfunctioning.
• The Brake ECM is malfunctioning.
• There is wear or damage to the hydraulic cylinders.
• There is wear or damage to the one-way check valves.
• There is wear or damage to the slack adjusters.
• There is air in the oil for the brake hydraulic system.
• There is wear or damage to the brakes.
• There are broken brake release springs.

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770G and 772G Off-Highway Truck (OEM) Hydraulic and Braking System: Brake System Troubleshooting 2013-01-22T12:34:00-08:00 Rating: 4.5 Diposkan Oleh: Unknown