Pontiac FIREBIRD 1972 Service Manual page 473

TANDEM DIAPHRAGM POWER BRAKE-BENDIX
5C- 13
3. Remove rear piston and spring assembly and discard.
Do NOT attempt to disassemble it since a complete
new assembly is provided in the repair kit.
4. Remove front piston assembly, front return spring
and retainer. Slide primary cup and protector off nose
of front piston. Use dull scribe to lift both secondary
seals from the grooves at the rear end of the piston.
Discard all old rubber parts.
CLEANING
Wash all hydraulic system parts in alcohol. Remove spots,
deposits or pitted areas inside the master cylinder bore
with crocus cloth. Discard all old rubber parts, except
reservoir diaphragm.
INSPECTION
Inspect all metal parts for damage or excessive wear. Re-
place any damaged or worn parts.
MASTER CYLINDER
ASSEMBLE (Fig. 5C-121
1. Clamp master cylinder in vise with open end tilted
slightly upward.
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 cup onto nose of front
piston.
3. Stack front piston return spring and retainer on nose
of front piston and dip assembly in brake fluid. Slide
assembly to bottom of master cylinder bore. Press
and twist piston to ease cups past snap ring groove.
4. 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.
5. Press in against rear piston with blunt tool to com-
press 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 sure snap ring is seated
securely in groove.
6. 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.
7. Remove master cylinder from vise. Install reservoir
diaphragm and cover and plug ports, temporarily, to
prevent entry of dust or dirt.
VACUUM SEAL IN REAR SHELL
ASSEMBLE
Place rear shell on block of wood, studs down, and using
seal installer J 22677, press new seal, plastic bearing face
first, into recess in rear shell. Top outside flange of seal
should be pressed .305" (approximately 5/16") below flat
shell surface next to seal cavity (Fig. 5C-13).
PLATES PLUNGER AND DIAPHRAGM
ASSEMBLE
Install front diaphragm on front plate.
Apply a light film of power brake lubricant to outside
surface of front plate and hub and liberally to the seal
in the center plate bore. Carefully guide center plate
and seal assembly, seal side first, onto front plate hub
using tool J 22733. (See Fig. 5C-14).
Install square ring seal firmly against shoulder of
front plate hub.
Apply power brake lubricant lightly to front and rear
bearing surfaces of valve plunger, being careful NOT
to get any lubricant on rubber grommet inside
plunger. Assemble valve plunger return spring on
5/16" BELOW FLAT
REAR BEARING
I
BEARING SEAL INSTALLER, J-22677
Fig. 5C-13 Installing Rear Shell Vacuum Seal