Chevrolet 30 Series 1967 Service Manual page 234

BRAKES 5-18
minimum. If the clearance is leSs than .035, the
primary cup should be replaced.
Assembly (Fig. 28)
Dual C ylinder
B rake C ylinder Side
NOTE: Moisten all parts except snap ring with
brake fluid as assembly progresses.
1. Carefully position check valve seat at outlet end of
cylinder bore.
2. Insert check valve; then the piston return spring with
primary cup expander toward open end of cylinder.
3. Install primary cup, skirt first. Take care that skirt
is not rolled back or torn during installation.
4. Insert piston with secondary cup toward open end of
cylinder. Same care to be observed on secondary cup
as on primary.
5. Install piston stop snap ring.
Clutch C ylind er Side
Replace same as brake cylinder except for replacement
of check valve and check valve seat.
Single C ylinder
NOTE: Moisten all parts except snap ring with
brake fluid as assembly progresses.
1. Install valve seat, valve, spring, and primary cup in
cylinder bore.
2. Install piston and secondary cup; secure with lock
ring.
Installation
D ual C ylinder (except Tilt Cab) (Fig. 1)
1. Reverse above applicable removal procedures.
.
2
Fill main cylinder reservoir end bleed brakes as
outlined in this section.
3.
Check operation of brakes and clutch.
4. Install cover on main cylinder.
Tilt Cab (Fig. 1)
1. Align pedal push rods, position cylinder against
mounting flange and bolt in place.
2. Slide end of rubber dust boots over cylinder tubes
and connect fluid lines.
3. Tilt cab down.
F ig . 31—S e lf Adjusting Brake
4. Fill cylinder and bleed brakes and clutch systems as
noted in above installation (except tilt cab).
5. Install cover on main cylinder.
. Adjust linkage if necessary.
6
Single C ylind er (Fig. 1)
1. Install boot in position and install main cylinder to
firewall with bolts, washers and nuts.
2. Connect hydraulic lines
cylinder.
3. Connect brake pedal return spring.
4. Fill main cylinder reservoir and bleed brakes as
outlined in this section.
5. Install cover on main cylinder.
BRAKE COMPONENTS-SELF ADJUSTING
FRONT AND REAR BRAKES
Brake shoe adjustment takes place when brakes are
applied with a firm pedal effort while vehicle is backing
up. Applying the brakes moves an actuator which turns
the star wheel and lengthens the adjusting screw assem­
bly (fig. 31). This action adjusts the shoes until clearance
between the lining and drum is within proper lim its.
Should low pedal heights be encountered, it is rec­
ommended that numerous forward and reverse stops be
performed with a firm pedal effort until a satisfactory
brake pedal height results.
NOTE: Frequent usage of an automatic trans­
mission forward range to halt reverse vehicle
motion may prevent the automatic adjusters
from functioning, thereby inducing low pedal
heights.
Retracting Self Adjusters
A lanced " knock out" area is provided in the web of
the brake drum on all models except the P20, P30 and 50
and the rear wheels of the K20 and C30. On these models
the access hole is located in the flange plate. This hole is
for service purposes in the event retracting of the brake
shoes is required to remove the drum. However, in order
to back off the adjuster, it will be necessary to hold the
actuating lever away from the starwheel (fig. 32).
Brake Drums, Shoes and Linings
NOTE:
If brake drums are worn severely, it
may be necessary to retract the adjusting screw
as previously outlined.
CAUTION: After knocking out the metal, be
sure to remove it from the inside of the drum
and clean all metal from the brake compartment.
A new hole cover must be installed when drum
is reinstalled.
^
Removal
1. Raise the vehicle and place on stand jacks.
2. Loosen check nuts at forward end of parking brake
cable sufficiently to remove all tension from brake
cable.
3. Remove brake drums.
NOTE: Since boots are recessed in grooves on
wheel cylinders to prevent pistons from leaving
cylinders, it is not necessary to install wheel
cylinder clamps when brake shoes are removed;
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at dash, toe pan, and
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CHEVROLET TRUCK SERVICE M ANUAL