Chevrolet 30 Series 1967 Service Manual page 224

BRAKES 5-8 #
Fig. 15—Brake Pedal Free M ovem ent—G 10-20
. Open bleeder valve 3/4 turn and observe flow. When
6
bubbles no longer appear and fluid flows in a solid
stream, close valve securely.
7. Repeat operations 4, 5 and
system.
. Apply approximately 75 pounds pressure on the
8
brake pedal and check the pedal clearance from the
toe board to the forward edge of the pedal pad. This
clearance should be a minimum of 5 inches with the
floor mat removed. If reserve is less than 5 inches,
rebleed the entire system in the sequence outlined
above.
Manual Bleeding—Single System
(Single Reservoir Main Cylinder)
Manual bleeding is sim ilar to pressure bleeding except
that the brake fluid is forced through the lines by pumping
the brake pedal instead of by air pressure.
1. Clean all foreign matter from main cylinder re se r­
voir area and remove reservoir cover.
2. Fill main cylinder reservoir.
3. In sequence, bleed wheel cylinder in the following
manner. Position bleeding tube J-0628 over end of
first bleeding valve in sequence indicated. Place
other end of tube in transparent container holding
sufficient fluid to cover end of tube.
4. Open bleeder valve approximately 3/4 of a turn, de­
press the brake pedal a full stroke and allow it to
return slowly, making sure the end of the bleeder
tube is under the surface of the liquid in the con­
tainer. Continue operating the pedal, refilling the ja r
at the main cylinder when necessary, until liquid
containing no air bubbles emerges from the bleeder
tube. Close bleeder valve as brake pedal is on down
stroke.
5. Replace reservoir cover then readjust all brake
shoes.
. Apply approximately 75 pounds pressure on the
6
brake pedal and check the pedal clearance from the
at each bleed valve in
6
toe board to the forward edge of the pedal pad.
This clearance should be a minimum of 5 inches with
the floor mat removed. If reserve is less than 5
inches, rebleed the entire system as outlined.
PARKING BRAKE CABLE—LUBRICATION
Parking brake cables should be lubricated during a
brake reline job or when adjusting brakes if cables feel
stickly.
When lubricating the brake cables, the rear brake
drums must be removed on 1/2 and 3/4 ton vehicles in
order to make sure that lubricant is not forced into the
brake assembly during lubrication.
BRAKE PEDAL-TO-FLOOR CLEARANCE
Any time the brake pedal-to-floor reserve is less than
shown below, the brake system should be immediately
checked for malfunctions. Refer to Figure 16.
NOTE: Brake pedal reserve measurements to
be made with 75 lbs. pressure on brake pedal.
Take measurement with engine not running when
truck has standard or optional power brakes,
and with engine running when truck has standard
power brakes.
BRAKE PEDAL ADJUSTMENT—G10-20 SERIES
(Fig. 15)
1. Loosen check nut on the eccentric bolt attachment
between the brake pedal and main cylinder push
rod.
2. Turn eccentric bolt as required to provide correct
adjustment. Movement of pedal pad before push
rod contacts main cylinder piston must be 1/16" to
1/4" (fig. 5).
NOTE:
Eccentric Adjustment bolt should be
installed with projection in up position before
adjustment.
\
Fig . 16—Brake Pedal Reserve Measurement
CHEVROLET TRUCK SERVICE M ANUAL