5B-2
1968
PONTIAC
SERVICE
MANUAL
SWITCH ADJUSTMENT
WITH PEDAL RELEASED, ADJUST SWITCH
SO
THAT
PLUNGER
IS
FULLY DEPRESSED AGAINST PEDAL
Fig.
5B-1
Power Brake
System
4. Using tool J 9504, press down firmly and rotate
tool and housing clockwise so that
cut-
outs
in
rear
housing line up with indentation of front housing.
NOTE:
Remove rear housing carefully as it is
spring-loaded and will
tend
to fly
away
from the
front housing.
5. Remove tool, housing, hydraulic push rod from
diaphragm
plate (power piston) and return spring
from
front housing.
6. If check valve
needs
replacing, push it and the
grommet out of the front of the housing.
7. Remove assembly from vise and remove master
cylinder
assembly or Tool J-22805-01 from front
housing.
8. Remove front vacuum seal with a blunt tool.
2.
Remove the two felt air silencers and the one
foam type filter. Be careful not to chip plastic
housing.
3.
Remove diaphragm plate (power piston) from
rear
housing.
4.
Carefully
remove rubber diaphragm from
dia-
phragm
plate.
5.
Tilt
diaphragm plate and depress valve operat-
ing rod slightly to remove valve assembly retainer
(valve plunger
stop
key). See Fig. 5B-3.
6.
Pull
control valve assembly straight out from
diaphragm
plate and with a blunt tool, push reaction
disc
out front of plate. Do not disassemble control
valve assembly.
7. Inspect
rear
vacuum seal. Remove only if nec-
essary
to replace by driving out with a screwdriver
or
punch.
POWER PISTON-DISASSEMBLE
(Fig. 5B-4}
CAUTION:
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 pro-
tected
from nicks or cuts
that
might
be caused by
rough surfaces or
damaged
tools.
1. Remove
boot
and felt filter from power unit.
MASTER CYLINDER-DISASSEMBLE
(Fig. 5B-5)
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
O-
ring
seal. Maintain pressure on
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