Master Cylinder - Chevrolet LIGHT DUTY TRUCK (SERIES 10-35) Service Manual

BAIL
COVER
STOP
S C R E W
RESERVOIR
D I A P H RAG M
TUBE SEAT
INSERTS SPRING
SPRING RETAINER
PRIMARY SEAL
S E C O N D A R Y PISTON
S E C O N D A R Y SEALS
Fig. 5-14--Delco M aster C ylin d e r-E xp lo d e d V iew
nut. Tighten the nut to 22-30 ft. lbs. and install a NEW
cotter pin.
11. Fasten the boot to the floorpan and compress the
boot to 2.54" installed height; tighten the boot to 2.54"
installed height; tighten the boot screws to 13-18 in. lbs.
(Refer to Figure 5-13).
12. Adjust brake pedal and stoplamp switch as outlined
previously.
P30(42) and G Models
Replacement
1. Remove the brake pedal striker screw
G Models-
and remove the striker. Remove the cotter pin and washer
and disconnect the pedal rod from the brake pedal.
.
2 P30(42) Models-
bolt to disconnect the pedal rod from the brake pedal.
3. Remove the pedal rod retainer bolt (at the rod pivot)
and remove the retainer.
4. Remove the cotter pin and washer and remove the
pedal rod.
5. To install a new rod, reverse Steps 1-4 above.
Lubricate pivot points with Delco Brake Lube (or
equivalent).
CAUTION: See "Caution" on Page 1 of
this section.
. Check brake pedal and stoplamp switch adjustments
6
as outlined previously.

MASTER CYLINDER

Filling Brake Master Cylinder
The master cylinder must be kept properly filled to
insure adequate reserve and to prevent air from entering the
hydraulic system. However, because of expansion due to
heat absorbed from brakes and from engine, master cylinder
PRIMARY
PISTON ASSY.
LOCK RING
Remove the cotter pin nut and
Fig. 5 -1 5 -D e lc o Secondary Piston - Exploded V iew
must not be overfilled.
The brake fluid reservoir is on the master cylinder
which is located under the hood on the left side of the dash.
Thoroughly clean reservoir cover before removal to
avoid getting dirt into reservoir. Remove cover and
diaphragm. Add fluid as required to bring level to 1/4"
(plus or minus 1 / 8 ") from the lowest portion of the top of
each reservoir. Use Delco Supreme No. 11 Hydraulic Brake
Fluid or equivalent.
Do not use shock absorber fluid or any other fluid
which contains mineral oil. Do not use a container which
has been used for mineral oil or a container which is wet
from water. Mineral oil will cause swelling and distortion
of rubber parts in the hydraulic brake system and water will
mix with brake fluid, lowering the fluid boiling point. Keep
all fluid containers capped to prevent water contamination.
Except Bendix Mini-Master Cylinder
Removal
1 . Disconnect brake pipes from master cylinder and
tape end of pipes to prevent entrance of dirt.
2.
Manual brake only-
from master cylinder push rod.
3. Remove two nuts holding master cylinder to dash
or power cylinder and remove master cylinder from vehicle.
Be careful not to drip brake fluid on exterior paint.
Disassembly (Figs. 5-14 and 5-15)
1 . Clean outside of master cylinder thoroughly.
Remove reservoir cover and diaphragm. Turn cylinder over
and pump push rod by hand to drain all brake fluid. Always
discard used fluid.
2.
Manual brake only--
cylinder to uncover push rod retainer. The retainer has a
small, depressed tab in the side. This tab must be pried up
to release retainer.
3. Depress piston and remove secondary piston stop
bolt from bottom of front fluid reservoir (if so equipped).
4. Place master cylinder in a vise so that lock ring can
be removed from groove in the inside diameter of bore.
Remove lock ring and primary piston assembly. Remove
secondary piston, secondary piston spring and retainer by
BRAKES 5-25
Disconnect brake pedal
Pull boot away from master
LIG H T T R U C K S ER V IC E MANUAL