FLANGE & MOUNTING GP 4350169 - Caterpillar

Probable Causes
Parking brake
Brake disc
Parking and secondary brake control valve
Parking brake controlRecommended Actions
Parking Brake
The parking brakes are engaged with springs and released hydraulically.
Review any active diagnostic codes and determine the cause of the diagnostic code. Make necessary repairs to the truck.
Make sure that the parking brake relay is not sticking. Clean or replace the parking brake relay if the relay is sticking.
Inspect the parking brakes for damaged components. Repair the parking brakes if damaged parts are present. Brake Disc
The brake discs turn with the wheel assembly. When the plates are pressed together with the brake discs, friction causes the wheel assembly and discs to stop moving. The brakes are environmentally sealed. The brakes do not require adjustment. Oil continually flows through the brake discs for cooling. The Duo-Cone Seal Gp prevents the cooling oil from leaking to the ground or transferring into the axle housing.
PRESSURE CHECK AT BRAKE PURGE SCREW The residual pressure for the 777G at the brake purge screw should be 106 kPa (15.4 psi) (front) and 65 kPa (9.4 psi) (rear). Low residual pressure may indicate a failed slack adjuster. High residual pressure may also indicate a failed slack adjuster or warped brake discs.
WARPED DISC CHECK To check for warped brake discs, rotate the wheel to see if the pressure fluctuates. If the pressure fluctuates while rotating the wheel, the brake discs are probably warped and should be replaced.
BRAKE COOLING OIL LEAKAGETo check for brake cooling oil leakage, block the brake cooling ports and pressurize each brake assembly to a maximum of 138 kPa (20 psi). Close off the air supply source and observe the pressure, that is trapped in the brake assembly, for 5 minutes. The trapped pressure should not decrease. Parking and Secondary Brake Control Valve
The parking and secondary brake valve controls the flow of oil to the parking brakes. The spring applied parking brakes are released by hydraulic pressure. The engine must be in operation to have oil pressure in the passage from the parking brake release pump section.