Buick LeSabre 1965 Service Manual page 543

BRAKES
MASTER CYLINDER 9 - 2 1
and polished drums do not wear
in as readily as turned drums and
are more likely to cause unequal
braking when new. To insure
maximum lining life, the refin-
ished braking surface must be
smooth and free from chatter or
tool marks.
Run-out of the refinished surface
of brake drum must not exceed
.005" t o t a l indicator reading.
Run-out (sideways wobble) of the
open edge of drum must not ex-
ceed .030".
d. Brake Drum Balance
During manufacture, brake drums
are balanced within 3 inch ounces
by fastening weights, as required,
near the rim. These weights must
not be removed.
After drums are rebored, or if
difficulty is experienced in main-
taining proper wheel balance, it
is recommended that brake drums
be checked for balance. Drums
out of balance more than 3 inch
ounces may be corrected by in-
stallation of service b a l a n c e
weights. Brake drums may be
checked for balance on most off-
the-car wheel balancers.
9 - 1 2 BRAKE WHEEL
CYLINDER OVERHAUL
1. Remove wheel, drum, and
brake shoes. Be careful not to
get grease or dirt on brake lining.
2. Disconnect brake pipe or hose
from wheel cylinder and cover
opening with tape to prevent en-
trance of dirt. Remove wheel cyl-
inder from backing plate.
3. Remove links, boots, pistons,
cups, cup expanders and spring
from cylinder. Remove bleeder
valve.
4. Discard rubber boots, ex-
pander assembly, and piston cups.
Thoroughly clean all other parts
with hydraulic brake fluid or a
good grade of alcohol. CAUTION:
Do not use antifreeze alcohol,
gasoline, kerosene, or any other
cleaning fluid that might contain
even a trace of mineral oil.
5. Inspect pistons and cylinder
bore for scores, scratches, or
corrosion. Light scratches may
be polished with crocus cloth.
Do not use emery cloth or sand-
paper. Slight corrosion may be
cleaned with fine steel wool and
alcohol. If scratches or corroded
spots are too deep to be polished
satisfactorily the cylinder should
be replaced since honing is not
recommended.
6. Dip internal parts in brake
fluid and reassemble wheel cyl-
inder. When installing piston cups
use care to avoid damaging the
edges.
NOTE: Front wheel cylinder pis-
tons and cups are 1-1/8" dia-
meter and rear wheel cylinder
parts are 1" diameter.
7. Install wheel cylinder on brake
backing plate and connect brake
pipe or hose.
8. Install brake shoes, drum, and
wheel, then flush and bleed hy-
draulic system (par. 9-6).
9. Adjust brakes (par. 9-7) then
road test car for brake perform-
ance (par. 9-4).
9 - 1 3 BRAKE MASTER
CYLINDER OVERHAUL
a. Removal of Brake Master
Cylinder
1. Disconnect brake pipe from
master cylinder and tape end of
pipe to prevent entrance of dirt.
2. Disconnect brake pedal from
master cylinder push rod by re-
moving safety washer and re-
tainer. See Figures 9-7 and 9-8.
3. Remove two nuts holding mas-
ter cylinder to dash panel and
remove cylinder from car. Be
careful not to drip brake fluid on
exterior paint.
4. Clean outside of master cyl-
inder thoroughly. Remove filler
cap and diaphragm, turn cylinder
over, and pump push rod by hand
to drain all brake fluid. Always
discard used fluid.
b. Disassembly of Brake
Master Cylinder
1. Remove rubber boot. Remove
lock ring, then remove push rod
with stop plate. See Figure 9-14.
2. Remove piston with secondary
cup, primary cup, spring, check
valve, and valve seat washer.
3. Discard boot, lock ring, piston
and rubber cups, spring, check
valve, and valve seat washer.
These parts are furnished in the
master cylinder repair kit (Group
4.649).
Make certain that compensating
port in cylinder is clear; how-
ever, do not run a wire through
port as this may result in leaving
a burr which will cut a groove in
primary cup.
4. Remove reservoir cover and
gasket. Thoroughly clean master
cylinder with alcohol. CAUTION:
Do not use anti-freeze alcohol,
gasoline, kerosene, or any other
cleaning fluid that might contain
even a trace of mineral oil.
c. Inspection of Brake Master
Cylinder
Inspect cylinder bore for scores,
scratches, or corrosion. Light
scratches in cylinder bore may be
polished with crocus cloth. Do_
not use emery cloth or sandpaper.
Slight corrosion may be cleaned
with fine steel wool and alcohol.
If scratches or corroded spots
are too deep to be polished satis-
factorily, the cylinder should be
replaced since honing is not rec-
ommended and oversize pistons
and cups are not furnished for
service.
Wheel and master cylinder bores
have a hard, h i g h l y polished