Specifications

Vehicle System Testing & Adjusting 55
Brake System
NOTE: If excessive force is applied to the brake
pedal, the pedal can be forced to the end of the
stroke. This is normal and should not be interpreted
as a problem.
Problem: Pedal resistance is not solid (spongy)
(under normal pedal pressure).
Probable Cause:
1. Air in the brake hydraulic system.
2. Brake valve is loose.
3. Servo piston seals worn or defective in brake
valve.
4. Piston seals worn or defective in drive axle brake.
5. Low oil level of reservoir.
Problem: Extra (excessive) pedal travel (under
normal pedal pressure).
Probable Cause:
1. Pedal adjustment is not correct.
2. Air in the brake hydraulic system.
3. Brake valve is loose.
4. Servo piston seals worn or defective in brake
valve.
5. Low oil level of reservoir.
6. Piston seals worn or defective in drive axle brake.
Problem: Brake will not make application.
Probable Cause:
1. Low oil level of reservoir of brake valve.
2. Air in the brake hydraulic system.
3. Linkage adjustment is incorrect or bent.
4. Defective brake valve.
5. Bent plates or discs in drive axle brake.
6. Piston seals worn or defective in drive axle brake.
Problem: Hard pedal.
Probable Cause:
1. Mechanical resistance at pedal or disc assembly.
2. Restriction in the brake line.
3. Defective brake valve.
4. Brake discs look like glass (glazed) or are worn.
Problem: Both brake disc assemblies will not
release all the way (drag).
Probable Cause:
1. Brake disc assemblies defective (stuck pistons).
2. Brake disc uneven (out of flat).
3. Restriction in the brake line.
4. Defective brake valve.
Problem: Brakes will not make application after
being bled.
Probable Cause:
1. Leak in hydraulic line or connection.
2. Damaged seals in the brake valve.
Problem: Brake oil low in master cylinder
reservoir, fluid must be added frequently.
Probable Cause:
1. Leak in hydraulic line or connection.
2. Damaged seals in the brake valve.
3. Leak in the disc assemblies.
Parking Brakes
Problem: Brake will not make application.
Probable Cause :
1. Parking brake assembly is out of adjustment.
2. Parking brake control cable is out of adjustment.
3. Worn brake band.