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5-34
1977 PONTIAC SERVICE MANUAL
5. Install snap rings.
6. Install the front wheels and lower the vehicle.
7. Add brake fluid to bring level within 1/4 inch of top
of master cylinder.
8. Test brake operation before moving vehicle. This
initial application is necessary to move the front shoes against
the disc, thereby "adjusting" the front brakes.
CALIPER OVERHAUL
Removal
1. Removal of the caliper for overhaul is the same as for
shoe and lining replacement except that it will be necessary
to disconnect the brake hose. (Refer to front brake hose
replacement).
2. First, disconnect the hose from the steel brake line and
cap the fittings to prevent dirt from entering the line or the
hose. Then, remove the U-shaped retainer from the hose
fitting. Withdraw the hose from the frame support bracket
and remove the caliper
--
with hose attached
--
to a work
bence for overhaul.
Disassembly
1. Before beginning disassembly, thoroughly clean the
exterior of the caliber using brake cleaner. Place the caliper
on a clean work surface.
2. Remove the brake hose from the caliper, discarding
the copper gasket. Check the hose for worn spots, cracks or
other signs of deterioration. Discard the hose, if damaged, to
be replaced with a new hose at reassembly. Drain brake fluid
from the caliper.
3. Use clean shop towels to pad the interior of the caliper
and remove the piston by directing compressed air into the
caliper inlet hole. See Fig. 5-53.
C AUT I 0 N: Use just enough air pressure to ease
the piston out of the bore. If the piston is blown
out--e ven with padding pro vided--it may become
damaged.
WARNING:
DO
NOT
PLACE
THE
FINGERS IN FRONT OF THE PISTON IN
AN ATTEMPT TO CATCH OR PROTECT
IT WHEN APPLYING COMPRESSED AIR.
THIS COULD
RESULT IN SERIOUS
INJURY.
4. Use a screwdriver to pry the boot out of the caliper.
Extend the screwdriver across the caliper bore, under the
boot, and pry up. Be careful not to scratch the caliper bore.
5. Use a piece of wood or plastic
--
a plastic toothpick
is ideal
--
to remove the piston seal from its groove in the
caliper bore. DO NOT USE A METAL TOOL O F ANY
TYPE FOR THIS OPERATION.
Cleaning and Inspection
1. The boot, piston seal, rubber bushings and sleeves are
to be replaced each time the caliper is overhauled. Discard,
do not bother to clean and inspect, these parts.
I
Fig. 5-53 Removing Piston
2. Clean all other parts in clean denatured alcohol or
brake cleaner. Use dry, filtered compressed air to dry parts
and blow out all passages in the caliper and bleeder valves.
The use of lubricated shop air will leave a film of mineral
oil on the metal parts. This may damage rubber parts when
they come in contact after reassembly.
3. Check the mounting bolts for corrosion, breaks in the
plating or other damage. Do not use abrasives in an attempt
to clean the bolts
--
replace them.
4. Carefully examine the piston OD for scoring, nicks,
corrosion and worn or damaged chrome plating. If any
surface defects are detected, replace the piston.
5. Check the bore in the caliper for the same defects as
the piston with the exception of plating damage. The piston
bore is not plated and stains or minor corrosion can be
polished with crocus cloth. Do not use emery cloth.
Thoroughly clean the caliper after the use of crocus cloth. If
the bore cannot be cleaned up in this manner, replace the
caliper.
Reassembly
1. Lubricate the bore in the caliper and the new piston
seal with clean brake fluid. Position the seal in the caliper
bore groove. Lubricate the piston with clean brake fluid and
assemble a new boot into the groove in the piston so that the
fold faces the open end of the piston. Insert the piston into
the caliper bore, using care not to unseat the seal and force
down to the bottom in the bore. This will require a force of
50 to 100 pounds. Position the OD of the boot in the caliper
counterbore and seat with tool No. J 22904. See Fig. 5-54.
2. Check the boot installation to make sure that the
retaining ring molded into the boot is not bent and that the
boot is installed fully, below the caliper face, and evenly all
around. Otherwise dirt or moisture may enter the bore and
cause damage or corrosion.
3. Install the brake hose in the caliper inlet using a new
copper gasket.
Installation
1. Installation of the caliper and mounting parts (rubber
bushing, sleeves, shoe and lining assemblies, and bolts) is the
same as for lining replacement except for the following:
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