Pontiac FIREBIRD 1972 Service Manual page 432

BRAKES
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GENERAL 5-29
Open pressure tank hose valve to apply fluid to mas-
ter cylinder under pressure that does not exceed 35
pounds. It is not necessary to pump the brake pedal
when using pressure tank.
When fluid flows from bleeder tube into glass jar in
a solid stream that is free of air bubbles, that particu-
lar cylinder and line are bled; tighten bleeder valve
securely and remove bleeder tube.
When bleeding operation is completed at all wheel
cylinders where needed, make sure that fluid level is
1/4" (plus or minus 1/8") from the lowest portion of
the top of each reservoir (see Fig. 5-1 I), install rubber
diaphragm and cover.
FLUSHING HYDRAULIC SYSTEM
It may sometimes become necessary to flush out the brake
hydraulic system due to the presence of mineral oil, kero-
sene, gasoline, carbon tetrachloride, etc., which will cause
swelling and/or deterioration of rubber piston cups and
valves so they become inoperative.
To flush hydraulic system, proceed as follows:
Attach bleeder tube and open bleeder valve at left
front wheel.
Flush out system thoroughly with clean brake fluid,
pumping the fluid from master cylinder reservoir and
out of wheel cylinder bleeder valve.
Repeat steps 1 and 2 at remaining wheel cylinders. To
ensure thorough flushing, approximately 1/2 pint of
fluid should be bled through each wheel cylinder.
Replace all rubber parts in master and wheel cylin-
ders. Thoroughly clean cylinders and pistons in al-
cohol before installing new parts. Remove all traces
of alcohol before installation.
After installing parts, fill system with recommended
brake fluid and follow steps 2 through 4 under
BLEEDING BRAKES to flush system of cleaning
solution and to bleed brakes. In doing this, pump
brake fluid from wheel cylinder bleeder valves until
clear fluid flows from bleeder tube and then continue
until no air bubbles emerge from bleeder tube.
Use only government and S.A.E. approved brake
fluid, such as Delco Supreme 11 or equivalent. Never
use "hydraulic fluid" as it has a petroleum or syn-
thetic base and is not intended for brake systems.
Never re-use brake fluid, or use fluid which is cloudy,
dirty, or has air bubbles.
Do not mix brake fluids.
Store brake fluid in a clean dry place in the original
sealed container. Cap container tightly, do not use it
for other purposes, do not puncture a "breather
hole".
Use only clean brake fluid to flush the hydraulic
system. Dissassembled brake parts may be cleaned
with alcohol provided all traces are removed.
Before opening master cylinder remove dirt from
around cap.
PARKING BRAKE
The rear brake assemblies serve a dual purpose in that
they are utilized both as a hydraulically operated brake
and a mechanically operated parking brake. In view of this
dual purpose, the hydraulic brake must be properly ad-
justed as a base for parking brake adjustment.
NOTE: Automatic brake adjosters nonnaly
keep the parking brake adjosted correctly.
However, there may be a condition where the
parking brake system will require additional
adjostment even though the service brakes are
perfectly satisfictory.
INSPECTION, CLEANING AND LUBRICATION
If parking brake will not release completely unless the
pedal is forcibly returned to its position, or if the applica-
tion effort is high, check parking brake pedal assembly for
free operation.
If operation is sticky or a bind is experienced, correct as
follows:
1. Clean and lubricate cables (within conduits) and ca-
ble contact areas with lithium soap grease or equiva-
lent.
BRAKE FLUID PRECAUTIONS
Brake fluid is adversely affected by contamination from
dirt, automotive petroleum products and water absorbed
from the atmosphere. Contaminants can plug parts of the
hydraulic system, cause rapid wear or swelling of rubber
parts, and lower the boiling point of the fluid. The follow-
ing precautions should be observed when dealing with
brake fluid:
2. Inspect parking brake pedal assembly for straightness
and alignment.
3. Clean and lubricate parking brake pedal assembly
with bearing or chassis grease.
4. Check routing of cables for kinks, binds and broken
strands.