Buick LeSabre 1965 Service Manual page 566

9 - 4 4 POWER BRAKES BRAKES
SEAL
Figure 9-41—Removal of Bearing Seal
from Rear Housing
d. Trouble-Shooting
Power Brakes
Many brake troubles which are
blamed on the power brake unit
may actually be caused by a de-
fect outside of this unit. Brake
trouble-shooting procedure is
provided in paragraph 9-5.
9 - 2 5 DISASSEMBLY OF
POWER BRAKE
1. Place power brake unit in a
vise with push rod up. Clamp unit
firmly on sides of master cylin-
der reservoir.
2. Remove rear retainer and boot
and then reinstall nuts on rear
housing studs. Scribe a line be-
tween front and rear housings.
Using pry bars as shown in Fig-
ure 9-40, rotate rear housing so
that cutouts in rear housing line
up with tangs of front housing.
CAUTION: Loosen rear housing
carefully as it is spring-loaded.
3. Lift rear housing aosembly and
power piston assembly from unit.
Then remove power piston return
spring.
4. Remove power piston assem-
oly from rear housing and lay
power piston aside in a clean
place. NOTE: Do not remove
bearing seal from rear housing
unless seal is defective and new
seal is available. To remove
seal, support rear housing and
drive out seal with punch or
screwdriver. Discard seal. See
Figure 9-41.
5. Remove the master cylinder to
front housing attaching nuts and
separate the m a s t e r cylinder
from the front housing.
6. From the front housing remove
the seal, and if defective, the vac-
uum check valve. A l s o , place
master cylinder push rod with
front housing group. See Fig-
ure 9-42.
7. From power piston, pry off
filter retainer and remove air
silencer with air filter from valve
housing, being careful not to chip
p l a s t i c housing. Remove dia-
phragm from power piston, then
remove valve retainer lock key,
valve and rod assembly. Press
out reaction disc from diaphragm
plate. See Figure 9-43.
8. From the master cylinder re-
move snap ring, piston assembly,
Figure 9-42—Removal of Seal, Push
Rod and Check Valve
primary cup, spring and retainer,
residual check valve and reser-
voir cover. Then remove dia-
phragm from reservoir cover. If
secondary cup is damaged or
worn, remove cup from piston.
Use suitable tool to pry cup out
of groove and off piston. See Fig-
ure 9-44.
9 - 2 6 CLEANING AND
INSPECTION OF
PARTS
After disassembly, immersion of
all metal parts in Del-clean or
equivalent is recommended.
Plastic parts and parts containing
rubber should be cleaned only in
alcohol. Care should be taken to
prevent chipping of or damage to
plastic parts. All rubber parts
should be replaced. After parts
have been thoroughly cleaned,
those parts which come in con-
tact with brake fluid should be
rewashed in clean alcohol before
assembly. Use air hose to blow
out dirt and cleaning solvent from
recesses and internal passages.
When overhauling the master cyl-
inder, use all parts furnished in
the master cylinder repair kit.
DISCARD ALL OLD RUBBER
PARTS.
Inspect all other parts for dam-
age or excessive wear. Replace
any damaged, worn or chipped
parts. Inspect master cylinder
bore for scoring, rust, pitting or
etching. Any of these will require
replacement or reconditioning of
the master cylinder. If master
cylinder is replaced or recon-
ditioned, thoroughly clean master
cylinder bore with alcohol and
blow out all passages with com-
pressed air.