Bleeding The Hydro-Boost System - GMC G Service Manual

5A1-8 HYDRAULIC BRAKE BOOSTER SYSTEMS
5. Nut (14). Leave finger tight.
6. Bolt (16) and washer (11); bolt must be installed with
head on inboard side of vehicle.
7. Nut (10). Leave finger tight.
Tighten
• Nuts (10, 14 and 19) to 34 N*m (25 ft. lbs.).
8. Brake pedal rod. Refer to HYDRAULIC BRAKES
(SEC. 5A).
9. Master cylinder (2).
10. Nuts (12).
Tighten
• Nuts (12) to 34 N*m (25 ft. lbs.).
11. Hydraulic lines.
• Bleed the booster. Refer to "Bleeding the Hydro-
Boost System" in this section.
BLEEDING THE HYDRO-BOOST
SYSTEM
Whenever the booster is removed and reinstalled, the
steering system should be bled.
NOTICE: The power steering fluid and brake
fluid cannot be mixed. If the brake seals contact
steering fluid or the steering seals contact brake
fluid; seal damage will result.
1. Fill the power steering pump reservoir to the proper
level and let the fluid remain undisturbed for at least
two minutes.
2. Start the engine and run momentarily.
• Add fluid, if necessary.
3. Repeat steps 1 and 2 until the fluid level remains
constant after running the engine.
4. Raise the front of the vehicle so the wheels are off the
ground.
• Support the vehicle with suitable safety stands.
5. Turn the wheels from stop to stop, lightly contacting
the stops.
• Add fluid, if necessary.
6. Lower the vehicle.
7. Start the engine and depress the brake pedal several
times while rotating the steering wheel from stop to
stop.
8. Turn the engine off and pump the brake pedal 4-5
times.
9. Check brake fluid level. Add fluid if necessary.
10. If the fluid is extremely foamy, allow the vehicle to
stand a few minutes with the engine off. Then repeat
steps 7, 8 and 9.
11. Check for the presence of air in the oil. Air in the oil
will give the fluid a milky appearance. Air in the sys­
tem will also cause the fluid level in the pump to rise
when the engine is turned off. If it becomes obvious
that the pump will not bleed the air after a few
attempts, refer to POWER STEERING (SEC. 3B3) for
further diagnosis.