5C-6
1968
PONTIAC
SERVICE
MANUAL
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 round-end rod
to compress
return
springs. Do NOT use screw-
driver
or other sharp-edged tool since this
will
damage the push rod seat inside the piston. Maintain
pressure
on piston and use
Tru-Arc
pliers to install
snap
ring
in
groove
inside bore. Make sure snap
ring
is seated securely in groove.
6.
Install
piston
stop
screw and new
O-
ring
seal
in
port underneath bore. Torque screw with 3/8"
wrench
to 40 lbs. in.
7.
Install
new spring and check valve in both outlet
ports unless master cylinder is to be used on disc
brake
equipped vehicle. Press new tube seat into
each
port using spare tube nut. Make sure tube seat
is bottomed in port. Torque tube nut to 40 lbs. in.
to be sure tube seat is bottomed in port.
8. Remove master cylinder from vise.
Install
reservoir
diaphragm and cover and plug ports,
temporarily,
to prevent entry of dust or
dirt.
ASSEMBLY
OF
VACUUM
SEAL
IN
REAR SHELL
(Fig.
5C-7J
Place
rear
shell on block of wood, studs down, and
press new seal, plastic bearing face first, into re-
cess
in
rear
shell. Top outside flange of seal should
be pressed .305" (approximately 5/16") below flat
shell
surface next to seal cavity.
ASSEMBLY
OF
PLATES
PLUNGER
AND
DIAPHRAGM
(Fig.
5C-4)
Install
front diaphragm on front plate. Apply a
light film of power brake lubricant to outside surface
of front plate 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. 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 valve
plunger as shown and set spring and plunger in re-
cess
of front plate hub, grommet side up. Place
vacuum
seal firmly against shoulder on outside of
front
plate hub. Set
rear
plate, threaded bore down,
over valve plunger and, using hands only, screw
rear
plate
onto
front plate hub. To tighten plates,
place
1-1/16"
hex bar stock or tool J-22839 in vise
and
set plate assembly, front plate down, on hex
bar.
Using air channel slot or
rear
plate
edges,
hand
torque plates to 12 1/2 lb. ft. Remove plate
assembly from vise.
Install
rear
diaphragm on
rear
plate and over lip of center plate. Assemble
rear
diaphragm
spring retainer over
rear
diaphragm and
lip
of center plate. Using fingers, press retainer
onto
center plate until it
seats
against shoulder of
center plate.
ASSEMBLY
OF
DIAPHRAGMS
AND
PLATES
IN
FRONT
AND REAR SHELLS
(Fig. 5C-3)
Apply
power brake lubricant liberally to bearing
seal
in
rear
shell. Apply power brake lubricant
liberally
to scalloped cut-outs on
edge
of front shell.
When
assembling diaphragm and plate assembly in
rear
shell, the
rear
diaphragm and center plate lugs
must be aligned between lances on
rear
shell.
Care-
fully
guide valve housing
sleeve
through bearing seal
in
rear
shell, keeping diaphragm and plates in cor-
rect
alignment.
Work
outer rim of front diaphragm
into
rear
shell so that outer rim of front diaphragm
is under each of retaining lances on
rear
shell.
1. Secure power section front shell to tool J-8433
and
J-6407-02
as in Fig. 5C-3.
2.
Assemble
rear
shell to spanner wrenches
J-9504 as shown in Fig.
5C-3
0
3.
Secure front shell to arbor press.
4. Place power diaphragm
return
spring in front
shell,
small coil first.
5. Position
rear
shell, spanner wrenches, and tool
J-22553-1 over spring so that scribe marks
will
be
aligned when the shells are locked together.
6. Slowly compress assembly keeping in a
parallel
plane.
7. When front and
rear
shells are mated rotate
spanner
wrenches until the two shells are locked
together.
CA
UTION:
Do not
compress
assembly
to the
point
of
damaging
power
unit.
8. Release pressure from assembly and remove
all
tools
from front and
rear
shells.
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