Hummer H1 Service Manual page 451

7-12 Brake System
MASTER CYLINDER BLEEDING
NOTE: Master cylinder must be filled and kept at least half
full during bleeding operation (Figure 7-9).
1. Depress brake pedal slowly and hold. Loosen front brake
line to purge air from the front section of the reservoir.
2. Tighten front brake line and release brake pedal.
3. Repeat steps 1 and 2 until front reservoir is purged of air.
4. Repeat steps 1 through 3 for rear reservoir with rear brake
line.
5. Bleed brake system.
MASTER CYLINDER BENCH BLEEDING
NOTE: Master cylinder must be filled and kept at least half
full during bleeding operation. Perform this procedure prior to
installing master cylinder on vehicle.
1. Secure master cylinder flange in vise.
2. Remove cover and fill reservoir with DOT 3 brake fluid.
3. Screw threaded end of bleeder hose into brake line port on
master cylinder and insert opposite end into reservoir.
Repeat step for other bleeder hose (Figure 7-9).
4. Slowly push piston into master cylinder. Do not release
piston. Air will be forced into hoses. Repeat as needed
until no bubbles noted from lines. Lines must stay in fluid
until installed.
5. Refill reservoir with DOT 3 brake fluid and repeat step 4
until no air bubbles remain in brake fluid.
6. Remove bleeder hoses from brake line ports on master
cylinder.
7. Install cap on master cylinder and remove from vise.
8. Install master cylinder.
9. Bleed brake system.
_____________________________________________________________
CAP
MASTER CYLINDER
FLANGE
PISTON
VISE
Figure 7-9: Bench Bleeding Master Cylinder
®
RESERVOIR
BLEEDER
HOSES