Pontiac FIREBIRD 1972 Service Manual page 457

5B-10 1972 PONTIAC SERVICE MANUAL
Fig. 58-8 Valve Plunger Stop Key
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Remove and Install
apparent, master cylinder must be replaced. If it appears
that contaminants have damaged the bore, replace da-
maged parts and flush out entire brake system including
wheel cylinders.
The sealing surfaces should be clean and smooth. Check
for cracks and damaged threads. Be sure that the by-pass
and compensating ports to the master cylinder reservoirs
are not restricted.
Check for distortion of all springs and deterioration of all
rubber parts. Any evidence of soft or swollen rubber parts
indicates contaminated brake fluid, requiring flushing of
the entire brake system and replacement of wheel cylinder
cups as well as all rubber parts in master cylinder.
INSPECT AIR FILTERS
Replace air filters if dirty. Do not clean.
POWER UNIT AND MASTER CYLINDER
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ASSEMBLE
MASTER CYLINDER
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ASSEMBLE
1. Clamp master cylinder in vise with open end slightly
above horizontal.
2. Install new secondary seals, back to back, in grooves
on rear end of front piston. Dip seals in brake fluid
and lift them carefully into grooves with dull scribe.
Slide protector and primary cqp onto nose of front
piston.
Stack front piston return spring and retainer on nose
of front piston and dip assembly in brake fluid. Press
and twist piston to ease cups past snap ring groove
into bore. Slide assembly to bottom of bore.
Dip new rear piston and spring assembly in brake
fluid and slide assembly into bore. Use scribe and
press piston to ease cups into bore.
Press in against rear piston with rough-end rod to
compress return springs. Do NOT use screwdriver or
other sharp-edged tool since this will damage the
push rod seat inside the piston. Maintain pressure on
piston and use snap-ring pliers to install snap ring in
groove inside bore. Make certain that snap ring is
securely seated in groove.
Maintain pressure on rear piston while installing pis-
ton stop screw and new O-ring seal in port under-
neath bore. Torque screw with 3/8" wrench to 40 lb.
in.
Remove master cylinder assembly from vise.
POWER PISTON
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ASSEMBLE (Fig. 58-7)
1. If rear vacuum seal was removed, place rear housing
on bench with studs down and press new seal care-
fully into cavity in housing, plastic side first, using
tool J 22677. (Fig. 5B-9). Use hands to press seal
about 7/16" below inner housing surface or until
metal shoulder bottoms. DO NOT CRACK PLAS-
TIC.
2. Lubricate outside diameter of diaphragm plate hub,
bearing surfaces of the valve plunger, and outer edge
of valve poppet with power brake lubricant.
3. Insert control valve assembly into diaphragm plate
INSTALLER
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Fig. 58-9 Installing Rear Vacuum Seal