Chevrolet 30 Series 1967 Service Manual page 222

BRAKES 5-6
4. At other adjusting slot, repeat steps 2 and 3 to adjust
other shoe.
5. Install adjusting hole covers in backing plate.
BLEEDING BRAKES
The hydraulic brake system must be bled whenever any
line has been disconnected or air has in some way
entered the system. A ''spongy'' pedal feel when the
brakes are applied may indicate presence of air in the
system. The system must be absolutely free of air at all
times. Bleeding should be done on the longest line first;
the proper sequence to follow is left rear, right rear,
right front, and left front. Bleeding of brake system may
be performed by one of two methods—pressure or
manual.
Brake Fluid
Use GM Hydraulic Brake Fluid No. 11 or equivalent
when servicing brakes. This brake fluid is satisfactory
for any climate and has all the qualities necessary for
proper operation, such as a high boiling point to prevent
vapor lock and the ability to remain fluid at low
temperatures.
In the event that improper fluid has entered the system,
it will be necessary to service the system as follows:
1. Drain the entire system.
2. Thoroughly flush the system with clean alcohol, 188
proof, or a hydraulic system cleaning fluid such as
" Declene" .
3. Replace all rubber parts of the system, including
brake hoses.
4. Refill the system.
5. Bleed the system.
Dual System (Dual Reservoir Main Cylinder)
1. Clean all dirt from top of main cylinder and remove
cylinder cover and rubber diaphragm.
2. Reduce fluid level in main cylinder until reservoirs
are approximately half full.
NOTE:
Make sure brake fluid in bleeder equip­
ment is at operating level and that the equipment
is capable of exerting 30 to 50 lbs. hydraulic
pressure on the brake system.
3. Install brake bleeder adapter J - 22489 (fig. 11) on
main cylinder. Connect hose from bleeder equipment
Fig. 11—Brake Bleeder Adapter Tool J-2 2 4 8 9 Installed
to bleeder adapter and open release valve on bleeder
equipment.
4. Install brake bleeder wrench, Tool J-7647 on bleeder
valve at wheel cylinder and install one end of bleeder
5. Pour a sufficient amount of brake fluid into a trans­
parent container to insure that end of bleeder hose
will remain submerged during bleeding. Place the
loose end of bleeder hose into the container. Be sure
the hose end is submerged in the fluid.
. Open wheel cylinder bleeder valve by turning Tool
6
J-7647 counterclockwise approximately 1/3 of a turn
and observe flow of fluid at end of bleeder hose.
7. Close bleeder valve tightly as soon as bubbles stop
and brake fluid flows in a solid stream from the
bleeder tube.
. Remove brake bleeder wrench and bleeder hose from
8
wheel cylinder bleeder valve.
9. Repeat Steps 4 through
cylinders in the correct bleeding sequence.
10. Disconnect bleeder equipment from brake bleeder
adapter cover J-22489.
NOTE: The main cylinder on certain passenger
car models is tilted upward. When removing the
bleeder adapter on these models, place a clean
dry cloth behind and below the cylinder to absorb
any fluid spillage as the cover is removed.
11. Remove bleeder adapter J-22489. Wipe all area dry
of fluid if fluid was spilled during adapter removal.
12. Fill m aster cylinder reservoirs to within 1/4" of
reservoir rim s as shown in Figure 13.
13. Install main cylinder diaphragm and cover.
Dual System (Dual Reservoir Main Cylinder)
1. Clean all dirt from top of main cylinder and remove
cylinder cover and rubber diaphragm.
2. Fill main cylinder reservoir.
3. Install brake bleeder wrench, Tool J-7647 on bleeder
valve at wheel cylinder and install one end of bleeder
tube J-0628 on bleeder valve.
4. Pour a sufficient amount of brake fluid into a trans­
parent container to insure that end of bleeder tube
will remain submerged during bleeding. Place the
loose end of bleeder tube into the container. Be sure
the tube end is submerged in the fluid.
NOTE: Carefully monitor fluid level at main
cylinder during manual bleeding operations. Do
not bleed enough fluid at one time to drain the
reservoir completely. Replenish the reservoirs
Fig . 12—Brake Bleeder Tool J-7 6 4 7
on the remaining wheel
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CHEVROLET TRUCK SERVICE MANUAL