BRAKES-PARKING MOTOR TRUCK SERVICE MANUAL
operating pressure limits, will result in the spring brakes
in the removal of the parking brake and service brake
automatically applying the service brakes.
DO NOT attempt to perform any
1. Adequately block vehicle wheels to prevent
disassembly whatsoever of the parking brake with the
vehicle from rolling.
unit on the vehicle, even though the air pressure is
2. Release air pressure to parking brake and
exhausted and the parking brake spring is some what
decompressed as shown in Fig. 6. The parking brake
3. Remove air hoses from parking brake and
spring is by no means completely decompressed. It is
service brake chambers. Tag hoses for proper
still exerting a force of approximately 1200 lb. against
the head of the chamber.
4. Disconnect service brake piston rod from slack
Disassembly of the parking brake should be
performed with the unit on an arbor press or hydraulic
5. Remove parking and service brake assembly
press where adequate safety measures can be taken
from mounting bracket.
The following disassembly procedure is based on the
parking and service brake assembly being removed from
1. Remove the breather cap from end of parking
brake cylinder. This will expose the release bolt.
Fig. 8 Backing Off Release Bolt.
2. Back off parking brake release bolt located in
Fig. 7 Parking Brake Applied through Loss of Air
end of parking brake chamber, Fig. 8. This
Pressure and Service Brake Released with Release Bolt.
action will compress the parking brake spring
Fig. 7 illustrates release mechanism of the spring brake.
and at the same time allow the coil spring within
Note position of release bolt and push rod.
the service brake to decompress to a brake
REMOVAL From the information outlined under
"OPERATION", it can be readily seen that to avoid
Remove clamp ring securing parking
possible serious bodily injury and damage to the brake
brake chamber to service brake chamber, Fig.
assembly, no attempt should be made to disassemble
Separate parking brake chamber from
the parking brake with unit installed on the vehicle. The
service brake chamber.
parking brake should be removed from the vehicle as a
Reset or tighten release bolt.
complete assembly and moved to a suitable press where
adequate safety measures can be taken during
The following information will assist