GMC 1976 ZEO 6083 Maintenance Manual page 247

5- 28 BRAKES
CLEANING AND INSPECTION
1 . Inspect cylinder bore for scoring or corrosion .
It is best to replace a corroded cylinder.
NOTE :
Staining is not to be confused with corro-
sion . Corrosion can be identified as pits or exces-
sive roughness.
2. Polish any discolored or stained area with
crocus cloth by revolving cylinder on cloth sup-
ported by a finger . Do not slide cloth in a lengthwise
manner under pressure .
Do not use any other form of abrasive or abrasive
cloth .
3. Rinse cylinder in Declene or equivalent .
4. Shake excessive rinsing fluid from cylinder . Do
not use a rag to dry cylinder, as lint from the rag
cannot be kept from cylinder bore surfaces .
ASSEMBLY
1 . Lubricate cylinder bore and counterbore with
clean brake fluid and insert spring expander assem-
bly.
2 . Install new cups . (Be sure cups are lint and dirt
free). Do not lubricate cups prior to assembly .
3 . Install new pistons in the "as received" condi-
tion-do not lubricate pistons with brake fluid.
4. Press new boots into cylinder counterbores by
hand . Do not lubricate boots prior to assembly .
CALIPER OVERHAUL
DISASSEMBLY
Before beginning disassembly, thoroughly clean
the exterior of the caliper using clean Declene or
equivalent . Place the caliper on a clean work surface.
Remove the brake hose from the caliper, discard-
ing the copper gasket . Check the hose for worn spots,
cracks or other signs of deterioration. Discard the
hose, if damaged, replace with a new hose at reas-
sembly . Drain brake fluid from the caliper.
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 .
Figure 33-Removing Piston
Remove the piston by directing compressed air
into the caliper inlet hole . As shown in Figure 33 .
CAUTION : Use
just enough air pressure to
ease the piston out of the bore. Ifthe piston
is blown out-even with padding provided-
it may become damaged.
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 (figure 34).
Use a piece of wood or plastic to remove the
piston seal from its groove in the caliper bore . DO
NOT USE A METAL TOOL OF ANY TYPE FOR
THIS OPERATION.
Remove the bleeder valve from the caliper.
Figure 34-Removing Boot from Caliper