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5-40
1977 PONTIAC SERVICE MANUAL
3. Rotate screw to release spring tension and remove
front housing group.
Disassembly of Front Housing Group
1. Remove the power piston return spring. The retainer
plate may come out of the power piston return spring.
Remove the vacuum check valve and grommet from the front
housing, if the check valve is defective or the grommet
cracked, cut or damaged.
Fig. 5-60 Unlocking Front and Rear Housings
Disassembly of Rear Housing Group
1. Remove the boot and boot retainer from the rear
housing and push rod. Remove the felt silencer from inside
the boot.
2. Remove the power piston group from the rear housing
and remove the primary power piston bearing from the center
opening of the rear housing.
Disassembly of Power Piston Group
1. Remove the piston rod retainer and piston rod from
the secondary piston (Fig. 61).
NOTE: Due to an optional construction design on the
primary and secondary power pistons, special tool J
23101 will have to be reworked, as shown in Fig. 5-62.
2. Mount doubled-ended tool J 23101 (with large
diameter end up) in a vise. Position the secondary power
piston so that the two radial slots in the piston fit over ears
(tangs) of the tool. See Fig. 5-63.
3. Fold back primary diaphragm from the O.D. of the
primary support plate. Grip the edge of the support plate and
rotate counterclockwise to unscrew the primary power piston
from the secondary power piston. Note: It is possible that the
primary support plate will unlock from the primary piston
before the primary piston unscrews from the secondary
piston. If this happens, continue to turn the primary support
plate counterclockwise. Tabs ("stops") on the primary
support plate will temporarily lock the primary support plate
to the primary power piston and permit continued
counterclockwise rotation to unscrew the primary power
piston from the secondary power piston. See Fig. 5-65.
4. Remove the housing divider from the secondary
power piston. Remove the secondary power piston bearing
from the housing divider.
5. The secondary power piston should still be positioned
on tool J 23101. Jold back secondary diaphragm from O.D.
of secondary support plate. Grip the edges of the support
plate and rotate clockwise to unlock the secondary support
plate from the secondary power piston. See Fig. 5-65.
6. Remove the secondary diaphragm from the secondary
support plate.
7. Remove the reaction piston and reaction disc from the
center of the secondary power piston by pushing down on the
end of the reaction piston with a small object, such as a pencil,
wooden dowel, or metal rod. See Fig. 5-66.
8. Remove the air valve spring from the end of the air
valve (if it didn't come off during disassembly of the power
piston).
9. Mount Tool J 23 10 1 in a vise (with small diameter
end up). Position the primary power piston so that the two
radial slots in the piston fit over the ears (tangs) of the tool.
See Fig. 5-67.
10. Fold back primary diaphragm from the support
plate. Grip the edge of the support plate and rotate in a
counter-clockwise direction to unlock the primary support
plate from the primary power piston. See Fig. 5-68.
1 I. Remove the primary diaphragm from the primary
support plate.
12. Remove the air filter and push rod limiter washer
from the tubular section of the primary power piston.
13. Remove the power head silencer from the neck of
the power piston tube.
14. Remove the rubber reaction bumper from the end
of the air valve.
15. Using Truarc No. 2 pliers (J 4880), remove the
retaining ring from the air valve. See Fig. 5-69.
16. Remove the air valve-push rod assembly from the
tube end of the primary power piston. The following removal
methods are recommended:
(a) Place the primary power piston in an arbor press, and
press the air valve push rod assembly out the bottom of the
power piston tube with a rod not exceeding 1/2" in diameter.
(b) An alternate method would be the use of a heavy,
round shanked screwdriver. Insert screwdriver on both sides
of the push rod, and pull the air valve push rod assembly
straight out. A considerable force will be required.
(c) Another method requires the use of Truarc No. 22
pliers. Approximately 5/8" from the pointed ends of the
pliers, file or saw a small slot (approximately 1/32"
-
1/16"
wide and 1/10" deep) on each half of the pliers. Round off
the pointed ends of the pliers. Slip the slots in the pliers into
tangs on the control valve spring retainer. Grip the pliers and
pull the air valve push rod assembly straight out.
17. Removal of the air valve push rod assembly will
disassemble the control valve retainer.
18. Remover the " 0 " ring seal from the air valve.
19. Models using air valve push rod assemblies with a
formed eye on he end of the push rod will be serviced using
a complete assembly, since the floating control valve cannot
be removed over the eye end of the push rod.
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