Pontiac FIREBIRD 1972 Service Manual page 442

5A-6 1972 PONTIAC SERVICE MANUAL
I
I U A S I N G POSITION APPLYING POSITION
I
Fig. 5A-4 Removing Front Housing
2. Remove master cylinder and position it away from
the vacuum cylinder.
3. Scribe a line across front and rear housings to facili-
tate reassembly.
4. Install tool
J
22805-01 at front housing. Insert a 22"
long x 1 1/4" square channel tube in end of tool.
5. Using a 14" crescent wrench or equivalent, twist the
square channel tube counterclockwise enough to
separate front housing from rear housing (Fig. 5A-4).
6. Remove front housing and power piston return
spring.
POWER PISTON
REMOVE
1. Remove clevis pin retainer and pin at brake pedal.
2. Remove clevis and lock nut from push rod.
3.
Slowly pull power piston assembly out from the rear
housing, being careful not to damage the power pis-
ton bearing or push rod boot.
DISASSEMBLE (Fig. 5A-5)
CAUTION: Care must be taken in handling dia-
phragm of power piston group. Diaphragm
should be guarded against grease, oil and for-
eign matter and must be protected from nicks
or cuts that might be caused by rough surfaces,
damaged tools or dropping the piston.
1. Place power piston in vise, as shown in Fig. 5A-6.
Remove lock ring from power piston by prying from
under locking lugs.
2. Remove reaction retainer, vacuum cylinder push rod,
reaction plate, three reaction levers and air valve
spring (Fig. 5A-7).
3. Remove hydraulic cylinder push rod from center of
reaction retainer and O-ring seal from groove on the
rod.
4. Remove small reaction bumper and air valve spring
retainer from air valve. Remove power piston from
vise.
5. Place square end of tool
J
2 1524 in vise holding sup-
port plate and power piston with push rod facing up.
6. Pull diaphragm edges away from support plate and
position assembly on tool
J
21524 so that three lugs
on tool fit into three notches in power piston (Fig.
5A-8).
7. Press down on support plate and rotate counterclock-
wise until support plate separates from power piston
(Fig. 5A-9).
8. Remove diaphragm from support plate.
9. Remove foam air filter ring from outside of power
piston hub.
10. Position power piston in vise padded with shop tow-
els with hub end down.
CAUTION: Do not clamp on hub as outside
surface serves as bearing and sealing surface,
11. Remove snap ring on air valve using snap ring pliers
and place power piston with tube end down in arbor
press.
12. Press air valve from power piston hub using rod not
exceeding 1/2" diameter. Removal of valve releases
floating control valve, floating valve retainer, push
rod limiter washer and air filter materials (Fig. 5A-
10).
13. Remove O-ring seal from the air valve in second
groove from air valve operating rod end.