On-Vehicle Service; Pedal Travel; Stop Light Switch; Bleeding And Flushing Brakes - Chevrolet LIGHT DUTY TRUCK (SERIES 10-35) Service Manual

5-1 0 BRAKES

PEDAL TRAVEL

At reasonably frequent intervals, the brakes should be
inspected for pedal travel, which is the distance the pedal
moves toward the floor from a fully-released position.
Inspection should be made with the brake pedal firmly
depressed (approximately 90 lbs.) while the brakes are cold.
______ C-K-G Manual ........ 4.5"
______ C-K-G Power......... 3.5"
______ P (Except JF9) ...... 3.5"
__ ___ _P (JF 9 )............. 6.0"
On power brake-equipped vehicles, pump the pedal a
minimum of 3 times with the engine off before making pedal
travel checks. This exhausts all vacuum from the power
booster.

STOP LIGHT SWITCH

Adjustment
The design of the switch and valve mounting provides
for automatic adjustment when the brake pedal is manually
returned to its mechanical stop as follows:
1. With brake pedal depressed, insert switch and/or
valve assembly into tubular clip until switch body and/or
valve assembly seats on tube clip. Note that audible "clicks"
can be heard as threaded portion of switch and valve are
pushed through the clip toward the brake pedal.
2. Pull brake pedal fully rearward against pedal stop,
until audible "click" sounds can no longer be heard. Switch
and/or valve assembly will be moved in tubular clip
providing proper adjustment.
3. Release brake pedal, and then repeat Step 2 to assure
that no audible "click" sounds remain.
Electrical contact should be made when the brake
pedal is depressed 1.0-1.24" (C-K models), .45-.95" (G-P
models) from its fully released position.
BLEEDING AND FLUSHING BRAKE SYSTEM
Bleeding Brake Hydraulic System
A bleeding operation is necessary to remove air
whenever it is introduced into the hydraulic brake system.
It may be necessary to bleed the hydraulic system at
all four wheel cylinders if air has been introduced through
low fluid level or by disconnecting brake pipes at master
cylinder. If brake pipe is disconnected at any wheel cylinder,
then that wheel cylinder only need be bled. If pipes are
disconnected at any fitting located between master cylinder
and wheel cylinders, then all wheel cylinders served by the
disconnected pipe must be bled.
Manual Bleed
If the vehicle is equipped with power brakes, deplete
the vacuum reserve by applying the brakes several times.
1. Fill master cylinder with brake fluid and keep at least
one-half full of fluid during bleeding operation.
Bleed right rear brake, left rear brake, right front brake
and left front brake.
2. With the proper size box end wrench or Tool J-21472
over bleeder valve, attach bleeder tube to valve and allow
L IG H T TR U CK SER V IC E MANUAL

ON-VEHICLE SERVICE

tube to hang submerged in brake fluid in a clean glass jar
(fig. 5-1).
pedal.
to prevent air from being drawn through master cylinder.
entire system is to be bled.
repeat entire bleeding procedure if necessary.
Pressure Bleeding
type. That is, it must have a rubber diaphragm between the
air supply and the brake fluid to prevent air, moisture, oil
and other contaiminants from entering the hydraulic
system.
master cylinder.
Supreme # 11 brake fluid or its equivalent.
added.
master cylinder bleeder adapter and open the tank valve.
brake metering or combination valve to permit flow to the
front wheels. Therefore, it will be necessary to hold the valve
stem open manually pressure bleeding.
brakes, the valve stem must be either pushed in or pulled
3. Open the bleeder valve and fully depress the brake
4. Close bleeder valve and release brake pedal.
5. Repeat steps 3 and 4 until all air is evacuated.
Check and refill master cylinder reservoir as required
6 . Repeat the bleeding procedure at all wheels if the
7. Check the brake pedal, feel for "sponginess" and
Pressure bleeding equipment must be of the diaphragm
1. Install pressure bleeding adapter J-23518 to the
2. Make sure the pressure tank is at least 1/3 full of
The bleeder ball must be re-bled each time fluid is
3. Charge the bleeder ball to between 20 and 25 psi.
4. When ready to begin bleeding, connect hose to
5. Disc brakes require a manual override of the front
To hold the metering valve open to bleed the front
Fig. 5-1~Bleeding W heel C ylinder