Pontiac FIREBIRD 1972 Service Manual page 455

5B-8
1972 PONTIAC SERVICE MANUAL
VACUUM CHECK
VALVE GROMMET
CONTROL VALVE ASSEMBLY
(VALVE ROD 8 PLUNGER)
REAR HOUSING
DIAPHRAGM
Fig. 50-5 Power Unit
-
Exploded View
4.
Remove tool, housing, hydraulic push rod from dia-
phragm plate (power piston) and return spring from
front housing.
5 . Remove assembly from vise and remove tool J
22805-01 from front housing.
6. Remove front vacuum seal with blunt tool.
POWER PISTON
-
DISASSEMBLE (Fig. 58-7)
C AUTI 0 N :
Exercise extreme care in handling
power piston, rubber surfaces and metal parts
in this assembly. They should be guarded
against grease, oil and foreign matter and must
be protected from nicks or cuts that might be
caused by rough surfaces or damaged tools.
1. Remove boot and foam filter from power unit.
2. Remove the foam air silencers. Be careful not to chip
plastic housing.
3. Remove diaphragm plate (power piston) from rear
housing.
4. Carefully remove rubber diaphragm from diaphragm
plate.
5. Tilt diaphragm plate and depress valve operating rod
slightly to remove valve assembly retainer (valve
plunger stop key). See Fig. 5B-8.
6. Pull control valve assembly straight out from dia-
phragm plate and with a blunt tool, push reaction
disc out front of plate. Do not disassemble control
valve assembly.
7. Inspect rear shell vacuum seal. Remove only if neces-
sary to replace by driving out with a screwdriver or
punch.
MASTER CYLINDER
-
DISASSEMBLE
1. Pry splash seal and retainer out of shallow cavity
around master cylinder hub.
2. Press in against rear piston with round-end rod to
relieve spring load on piston stop screw under master
cylinder bore. Use 3/8" wrench to remove stop screw
and Olring seal. Maintain pressure on rear piston and
use snap ring pliers to remove snap ring from groove
in master cylinder bore.
3. Remove rear piston and spring assembly and discard.
Do not attempt to disassemble it since complete new