GMC 4000 Series Service Manual page 179

Sec. 5A
Page 172
HYDRAULIC BRAKES
1 R eservoir Cover
2 M aster Cylinder Housing
3 Piston Return Spring
4 Primary Cup
5 Piston Assem bly
6 Snap Ring
7 Boot
8 Check Valve (Brake Cylinder Only)
9 Check Valve Seat (Brake Cylinder Only)
10 Bleeder Valve (Brake Cylinder Only)
2. Fasten booster support bracket to fire wall
with four bolts.
3. Attach push rod to brake pedal.
4. If master cylinder only is to be installed
omit Steps 1, 2, and 3. Instead, place master cyl­
inder in position on studs on booster chamber and
fasten with two nuts.
5. Connect hydraulic brake line to master
cylinder.
6. Fill master cylinder reservoir with proper
fluid and bleed brake system as directed under
"Bleeding Brakes."
7. Adjust brake pedal push rod as necessary.
"S" MODELS
(SPLIT MASTER CYLINDER)
Removal (Refer to Fig. 11)
1. Wipe master cylinder and lines clean with
a clean cloth. Place dry cloths below master cyl­
inder to absorb any fluid spillage.
2. Disconnect hydraulic lines at master cyl­
inder. Cover line ends with clean, lint-free mater­
ial to prevent foreign matter from entering system .
G M C S E R V I C E M A N U A L
Figure 12— Double Barrel Master Cylinder Components
light wires and brake warning switch wire.
fasten master cylinder to dash. Pull master cylin­
out fluid from reservoirs. Pump the remaining
fluid out by depressing piston.
Installation (Refer to Fig. 11)
are in proper position.
bolts, and washers.
brake fluid.
heading of "Bleeding Brakes."
3. Disconnect battery ground strap or stop
4. Remove nuts, bolts, and washers which
der straight off push rod and remove from engine
compartment.
5. Remove and discard master cylinder push
rod boot.
6. Remove master cylinder cover and pour
1. Assemble new boot on brake pedal push rod.
2. Place master cylinder in position in engine
compartment. Make certain that push rod and boot
3. Fasten master cylinder to dash with nuts,
4. Connect brake lines to master cylinder.
5. Fill the reservoirs with recommended
6. Follow instructions in this manual under