Pontiac FIREBIRD 1972 Service Manual page 506

DISC BRAKES 5E-11
Fig. 5E-15 Removing Piston
CALIPER
REMOVE
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 at the caliper. Discard the cop-
per gasket on each side of the brass hose fitting.
DISASSEMBLE
1. Before beginning disassembly, thoroughly clean the
exterior of the caliper using alcohol.
2. Remove the bleeder valve from the caliper and drain
brake fluid from interior. Place caliper on a clean
work surface.
3. Use clean shop towels to pad the interior of the
caliper and remove the piston by directing com-
pressed air into the caliper inlet hole (Fig. 5E-15).
WARNING: USE JUST ENOUGH AIR PRESSURE
TO EASE THE PISTON OUT OF THE BORE. IF
THE PISTON IS BLOWN OUT- EVEN WITH PAD-
DING PROVIDED
-
IT MAY BECOME DA-
MAGED. DO NOT PLACE THE FINGERS IN
FRONT OF THE PISTON IN AN ATTEMPT TO
CATCH OR PROTECT IT WHEN APPLYING
COMPRESSED AIR; THlS 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 A N D INSPECTION
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.
Clean all other parts in alcohol or brake fluid. Use dry,
filtered compressed air to dry parts and blow out all pas-
sages in the caliper and bleeder valve.
WARNING: THE USE OF LUBRICATED SHOP
AIR WILL LEAVE A FILM OF MINERAL OIL ON
THE METAL PARTS. THlS MAY DAMAGE RUB-
BER PARTS WHEN THEY COME IN CONTACT
AFTER REASSEMBLY.
1. 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.
2. Carefully examine outside of piston for scoring,
nicks, corrosion and worn or damaged chrome plat-
ing. If any surface defects are detected, replace the
piston.
CAUTION: The piston 0 . D. is the primary seal-
ing surface in the callper assembly. It is manu-
factured and plated to close tolerances and
cannot be refinished or repaired.
3. Check the bore in the caliper for major defects with
the exception of plating damage. The piston bore is
not plated and stains or minor corrosion can be pol-
ished with abrasive cloth. Thoroughly clean the
caliper after the use of any abrasive. If the bore can-
not be cleaned up in this manner, replace the caliper.
ASSEMBLE
1. Lubricate the seal groove 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 move
piston until it bottoms in the bore. This will require
a force of 50 to 75 pounds.