Pontiac FIREBIRD 1972 Service Manual page 498

DISC BRAKES 5E-3
3. Master cylinder primary cup worn or damaged.
'
3. Repair master cylinder.
4. Master cylinder bore corroded, worn or scored. 4. Repair or replace master cylinder.
5. Caliper cylinder seals worn or damaged. 5. Replace seals.
6. Caliper cylinder bores corroded, worn or scored.
6. Disassemble caliper and remove corrosion or
scoring, or replace caliper.
7. Bleed screw open. 7. Close bleed screw and bleed hydraulic system.
NOISE A N D CHATTER (May Be Accompanied By Brake Roughness and Pedal
Pumping)
CAUSE CORRECTION
1. Disc has excessive lateral runout. 1. Replace or machine disc.
2. Disc has excessive thickness variations (out of 2. Replace or machine disc.
parallel).
3. Disc has casting imperfections. 3. Replace disc.
4. Car creeping or .moving slowly with brakes 4. Increase or decrease pedal effort slightly.
applied (may produce groan or crunching noise).
5. Squeal, during application. 5. A small amount of high-pitches squeal is inherent
in disc brake design and must be considered normal.
DRAGGING BRAKES (Slow or Incomplete Release of Brakes)
CAUSE
1. Lines, hoses or connections dented, kinked,
collapsed or clogged.
2. Master cylinder compensating port restricted by
swollen primary cup.
3. Residual pressure check valve in lines to front
wheels.
4. Caliper pistons frozen or seized.
5. Caliper cylinder seals swollen.
6. Caliper cylinder bores corroded or rough.
7. Hydraulic push rod on power brake out of
adjustment or binding (causing primary cup
to restrict master cylinder compensating port).
CORRECTION
1. Repair or replace defective parts.
2. Drain hydraulic system, flush system with
brake fluid and replace all cups and seals in
complete brake system.
3. Remove check valve.
4. Disassemble caliper and free up pistons (replace
if necessary).
5. Drain hydraulic system, flush system with clean
brake fluid and replace all cups and seals in
complete brake system.
6. Disassemble caliper and remove corrosion or
roughness, or replace caliper.
7. Adjust or free up and lubricate.
GENERAL DESCRIPTION
The single piston, sliding caliper, disc brake (Fig. 5E-1) is
standard equipment on all B, F and G Series models and
optional on the A Series. In addition, B and G Series
vehicles are equipped with power assist as standard equip-
ment.
The caliper assembly is constructed from a single casting
which contains one large piston bore in the inboard sec-
tion with a fluid inlet hole and bleeder valve hole connect-
ing directly to the piston bore.
The cylinder contains a piston and seal. A seal groove is
machined into the sidewall of the piston bore. The groove
is machined, so that it is shallower toward the bottom of
the piston bore. The purpose of this is to put more com-
pression on the edge of the square cut seal which faces the
brake fluid pressure. The seal is located in the groove and
fits around the outside diameter of the piston to provide
a hydraulic seal between the piston and cylinder wall.
The top of the piston bore is counterbored to accept a
sealing dust boot. The dust boot contains a metal retainer
as a part of the boot. The retainer part of the boot is
pressed into the recess in the top of the piston bore. The
inside diameter of the boot fits into a groove which is
machined in the piston.