5B-4
1968
PONTIAC
SERVICE
MANUAL
CONTROL
yVALVE
ASSEMBLY
f
OPERATING
ROD
VALVE
PLUNGER
•
STOP KEY
Fig.
5B-3
Valve Plunger Stop Key—Remove
and
Install
be free of scoring, rust, pitting or etching. If any
of
these
are apparent, master cylinder must be re-
placed.
If it appears that contaminants have dam-
aged
the bore, replace damaged 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 deteriora-
tion 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.
Fig.
5B-5
Master Cylinder—Exploded View
1. Snap Ring
2. Splash Shield
Retainer
3. Splash Seal
4. Secondary Seal
5. Rear Piston
and
Spring Assembly
6. Primary
Cup
7. Secondary Seals
8. Front (Floating)
Piston
9. Protector
10. Primary
Cup
11. Retainer
12. Front Piston Return
Spring
13. Piston Stop Screw
and Seal
14. Tube Seats
15. Check Valves
16. Springs
17. Master Cylinder
Casting
18. Hermetic
Diaphragm
19. Reservoir Cover
20. Bale-Type
Retainer
INSPECT
AIR
FILTERS
DIAPHRAGM DIAPHRAGM PLATE
RETURN
SPRING
(
POWER PISTON
)
DIAPHRAGM
Replace
felt
air filters if dirty. Do not clean.
POWER
UNIT
AND
MASTER
CYLINDER-ASSEMBLE
MASTER
CYLINDER-ASSEMBLE
(Fig. 5B-5)
1.
Clamp
master cylinder in vise with front end
slightly
below
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
cup
onto
nose
of front piston.
Fig.
5B-4
Power Piston—Exploded View
3.
Stack front piston return spring and retainer
on
nose
of front piston and dip assembly in brake
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