MOTOR TRUCK SERVICE MANUAL BRAKES-PARKING
15. After tightening clamp ring bolts, tap the ring with
2. When replacing spring brake chamber
a hammer to insure proper seating. Then
assemblies on early parking spring brake
recheck the nuts for tightness.
assemblies, always remove service brake
16. Replace air lines in their respective inlets.
chamber from mounting bracket. Also, remove
Apply air pressure and check for air leaks around fittings.
mounting plate and rubber insulator pad (Fig.
17. To reactivate the parking brake, apply air
20) from bottom exterior of service brake
pressure to the parking brake section and tighten
chamber. This will enable you to check service
release bolt to approximately 50 pounds torque,
brake chambers for damage or cracks-
particularly in mounting bolt areas. Replace with
18. Replace breather cap.
If breather cap is
new reinforced brake chambers if damaged.
equipped with a screen the hole must face
3. When reinstalling service brake chambers to
mounting brackets, do not use rubber insulator
19. Adjust service brakes after resetting parking
pad and mounting plate between brake chamber
and bracket. Proper mounting bolt nut torque
cannot be maintained with exterior pad and
1. Assemble parking and service brake assembly
mounting plate in this location. Tighten service
to vehicle mounting bracket.
brake mounting bolt nuts to 150 ft. lbs. torque.
2. Connect service brake piston rod to slack
3. Connect air supply hoses to their respective
inlets on parking brake and service brake
NOTE: Be certain to install correct hose in correct
4. Apply air pressure to parking and service brake
5. Remove vehicle blocking.
Whenever a spring brake chamber replacement is
made there are three important service precautions
which should be observed:
1. Do not use parking spring brake chambers on
chassis not already equipped with them unless
the service brake chambers are also changed to
the type having reinforcing plate inside the
service brake chamber (Fig. 20). Standard air
chambers do not provide sufficient strength in
mounting stud area to withstand added weight
Fig. 20 Early Model Parking Spring Brake Unit Having
and load imposed by the spring brake unit.
Mounting Plate and Rubber Pad
Every three months or 20, 000 miles add two ounces
of light engine oil (SAE10) into spring brake air inlet port.
Remove air inlet hose at spring brake chamber inlet port
and add oil into port. It will gradually work its way into the
cylinder and lubricate the seal. Under extremely cold
weather conditions, it may be necessary to pour an
ounce or two of antifreeze (Methanol) into the spring
brake air inlet port.