Chevrolet 30 Series 1967 Service Manual page 261

F ig. 76—Vacuum Booster Unit
The Hy-Power units are located with a bracket on the
truck chassis frame. The slave cylinder is located lower
than the master cylinder, and the bleeder screw on the
booster unit faces upward for ease of servicing. This
unit is inserted between the master cylinder and the
wheel cylinders.
2. Slowly open bleeder valve on power cylinder allowing
pedal to travel only 3/4 stroke. Close power cylinder
valve.
3. Repeat above operations until clear fluid containing
no air bubbles comes from this valve.
4. Bleed wheel cylinders in same sequence followed in
pressure bleeding.
Combination Pressure and Manual Bleeding
1. Connect bleeder tank to master cylinder.
NOTE:
2. Start engine and pump brake pedal three times or
until greatest pedal height is obtained and maintain
foot pressure.
3. Bleed power cylinder and wheel cylinders in same
sequence followed in pressure bleeding.
Fig. 77—Vacuum Booster Brake System
SERVICE OPERATIONS
FLUSHING
When installing or servicing a booster unit on a vehicle
which has had considerable service, flush entire hy­
draulic brake system to remove dirt and sludge. Inspect
master cylinder for defects and repair.
Be sure bleeder is filled with fluid and
charged to 25 psi air pressure.
BRAKES 5-47
For flushing
CHEVROLET TRUCK SERVICE M ANUAL