Chevrolet 10 Series 1968, Service Manual

Page: 336 / 713

BRAKES 5-93
1. Spanner Nut Retaining Washer
9. Washer 17. Housing to Plunger " O " Ring
2. Spanner Nut
10. Bolt 18. A ir Chamber Piston Plunger
3. Wedge Rod G uide
11. Non-Pressure Housing
Assembly
4. Tag Nut
12. Push Rod Boot
19. A ir Chamber Cap Assembly
5. Caution Tag
13. Diaphragm Plate Rod 20. Release Bolt Spring Lock
6. Nut
14. Rubber Diaphragm
21. Capscrew
7. Lock Washer
15. " F a il-S a fe " Pressure Housing 22. Lock Washer
8. Clam ping Ring
16. Housing to Cap Rubber Washer
Fig . 1 3 4 -"Fai 1-Safe" A ir Chamber Components
1
.
2
.
3.
4 .
5.
6
.
7.
9.
10.
With air pressure in parking brake chamber (brake
released), loosen release bolt spring lock and swing
to one side; then turn release bolt clockwise as far as
it will go (approx. 18 turns) to compress the power
spring. Refer to Figure 135.
Exhaust air pressure from parking brake chamber by
pulling parking brake knob out.
Disconnect air lines from both chambers.
Mark pressure housing and non-pressure housing so
that parts can be reassembled in the same relative
position. Loosen clamping ring by unscrewing bolt.
Hang clamping ring on non-pressure plate tube.
Remove entire cap and spring assembly, pressure
housing, and rubber diaphragm (See Figure 136).
Diaphragm plate rod and boot will remain in the non­
pressure housing.
Mount pressure housing in vise.
NOTE: Do not tighten vise jaws enough to dis­
tort pressure housing. Using a wrench on hex
end of cap, unscrew cap and spring assembly
from housing; OR mount hex end of cap in vise
and, using special "strap" type wrench to re ­
move pressure housing from cap assembly. See
Figures 137 and 138 for illustration of this op­
eration and dimensions to make a "strap" wrench.
Remove washer and O-ring from pressure housing.
Remove piston assembly from cap by pulling straight
out. At times the spring, when fully compressed,
cocks slightly. It is then necessary to loosen the re ­
lease bolt a few turns so that the piston can be with­
drawn easily.
The piston, retainer plate, seal and expander are held
together by rivets. If any part of this assembly is
defective the complete assembly must be replaced.
Details are not serviced separately.
Cap and spring assembly is serviced as a unit. If
any of the parts become damaged or need replacing,
it is necessary to replace the complete cap and spring
assembly.
CA U TIO N : Do not attempt to disassemble the
cap and spring assembly. In the event any part
of this assembly is defective, the complete as­
sembly must be replaced. The component parts
are no serviced separately.
F ig . 135-Compressing " F a il-S a fe " Power Spring
CHEVROLET TRUCK SERVICE MANUAL