Buick LeSabre 1965 Service Manual page 537

BRAKES
SERVICE 9 - 1 5
Figure 9-10—Right Wheel and
Brake Assembly
then close the bleeder valve se-
curely and remove bleeder tube.
4. Frequently check master cyl-
inder to make sure that it con-
tains fluid. Allowing reservoir
to be emptied will cause air to be
drawn into hydraulic systemT
5. When bleeding operation is
completed at all wheel cylinders
where needed, make sure that
fluid level is 1/8" below lip of
master cylinder filler opening;
then install rubber diaphragm,
cover, and retaining bail.
6. Discard the brake fluid depos-
ited in glass jar during bleeding
operation. It is poor economy to
attempt to clean fluid that has
once been used.
e. Bleeding Wheel Cylinder
with Pressure Tank
IMPORTANT: When using a pres-
sure tank, air bubbles may form
in the tank and enter the brake
hydraulic system. To avoid this,
observe the following points when
handling a pressure tank: (1) Do
not shake or agitate the pressure
tank after air pressure has been
added or is being added. (2) Al-
low pressure tank to stand in one
position as much as possible, and
bring air hose over to tank when
adding head of air. (3) Make cer-
tain the valves on the pressure
tank lines are not defective al-
lowing air to be sucked in when
fluid passes through the lines.
(4) Pressure tank should be kept
at least 1/3 full of fluid to avoid
air bubbles forming. (5) If pres-
sure tank is full of air bubbles,
release air pressure and bubbles
will increase in size, be forced
to top of fluid, and escape.
1. Thoroughly clean master cyl-
inder filler cap and surrounding
area; then remove cap and
diaphragm.
2. Make sure that pressure tank
is at least 1/3 full of specified
brake fluid, and that hose and
master cylinder reservoir are
filled with fluid. Attach hose to
m a s t e r cylinder r e s e r v o i r
adapter cover.
3. Install Wrench J-21472 on
bleeder v a l v e . Slip a brake
bleeder tube over ball of wheel
cylinder bleeder valve. Place
lower end of bleeder tube in a
clean glass jar. Unscrew bleeder
valve 3/4 of a turn. See Figure
9-10.
4. Open pressure tank hose valve
to apply fluid to master cylinder
under pressure that does not ex-
ceed 35 pounds. It is not neces-
sary to pump the brake pedal when
using pressure tank.
5. When fluid flows from bleeder
tube into glass jar in a solid
stream that is free of air bubbles,
that particular cylinder and line
are bled; tighten bleeder valve
securely and remove bleeder tube.
6. When bleeding operation is
completed at all wheel cylinders
where needed, make sure that
fluid level is 1/8" below top of
master cylinder filler opening.
Then install rubber diaphragm,
filler cap, and bail.
f. Flushing Brake Hydraulic
System
It is recommended that the entire
hydraulic system be thoroughly
flushed whenever new parts are
installed in the hydraulic system,
or new shoes or linings are in-
stalled. Flushing is also recom-
mended if there is any doubt as
to the grade of fluid in the sys-
tem or if fluid has been used
which contains the slightest trace
of mineral oil.
Flushing is performed at each
wheel cylinder in turn, and in the
same manner as the bleeding op-
eration except that bleeder valve
is opened 1-1/2 turns and the
fluid is forced through the pipes
and w h e e l c y l i n d e r until it
emerges clear in color. Approxi-
mately one quart of fluid is re-
quired to flush the hydraulic
system thoroughly.
When flushing is completed at all
wheel cylinders, make certain
that master cylinder reservoir is
filled to proper level.
9 - 7 BRAKE ADJUSTMENT
a. Preliminary Checks
1. Depress brake pedal firmly.
If pedal travels to within 2-1/4"
of toeboard on manual brake-
equipped cars or 1-1/2" of toe-
board on power brake-equipped
cars, brake shoes require ad-
justment or relining. However,
if pedal has a spongy feel, brake
system needs bleeding.
2. Remove one front wheel with
hub and drum assembly. Inspect
brake lining. If lining is worn
nearly to rivets, reline brakes
(par. 9-10).
3. Check fluid level in master
cylinder reservoir and add fluid
if necessary (par. 9-6).
4. Fully release parking brake
lever and place transmission in
neutral.
5. Pull on both ends of rear brake
cable a number of times to make