Steering System - Hummer H1 Service Manual

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1. Remove master cylinder cover and visually check reser-
voirs for low fluid level or contamination.
a. If fluid is contaminated, flush system with clean brake
fluid.
b. If fluid is low, check for worn brake pads, observe for
leakage, broken, cracked or kinked lines, worn master
cylinder, etc. Replace any worn parts. Add DOT 3 as
needed.
2. Check hydro-boost. Depress brake pedal several times,
with engine off, to exhaust accumulator pressure. Depress
brake pedal and start engine.
a. Brake pedal should fall, then push back against opera-
tor's foot.
b. Perform pressure test (Section 8).
c. Replace hydro-boost if not operating properly.
3. Bleed master cylinder then bleed brakes.
Decreased Brake Pedal Travel or Slow Return
1. Check for worn brake pedal return spring. Replace if
worn.
2. Check brake pedal bushings for signs of wear or binding.
Replace if worn and lubricate as needed.
3. Check for kinked or damaged brake lines which may
restrict brake fluid. Replace any damaged lines.
4. Check hydro-boost. Depress brake pedal several times,
with engine off, to exhaust accumulator pressure. Depress
brake pedal and start engine.
a. Brake pedal should fall, then push back against opera-
tor's foot.
b. Perform pressure test (Section 8).
c. Replace hydro-boost if not operating properly.
5. Check brake calipers for binding as a result of corrosion or
dirt. Check brake rotors for free movement. If rotors do
not move freely, remove calipers and clean caliper guide
pins.
6. Check parking brake cable for proper operation and
adjustment. Repair as required.
Excessive Pedal Pressure Required to Stop
Vehicle
1. Remove master cylinder cover and visually check reser-
voir for low fluid level or contamination.
a. If fluid is contaminated, flush system with clean brake
fluid.
b. If fluid is low, check for worn brake pads, observe for
leakage, broken, cracked or kinked lines, worn master
cylinder, etc. Replace any worn parts.
2. Check fluid in power steering pump reservoir. Fill fluid to
proper level (Section 1).
3. Check serpentine belt tension. Replace belt (Section 8) if
necessary.
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4. Check brake pads for proper installation, contamination,
or distortion. Check brake pads for excessive wear.
Minimum brake lining thickness is 1/8 in. (3.2 mm).
Replace brake pads as axle sets (front or rear) if any pad
does not meet specifications
NOTE: To preserve even braking, both calipers must be in
equal condition.
5. Check brake calipers for binding as a result of corrosion or
dirt. Check brake rotors for free movement. If rotors do
not move freely, remove calipers and clean caliper guide
pins.
6. Check for frozen piston in brake caliper. If inner pad is not
worn to limit, but piston cannot be retracted, rebuild or
replace both calipers.
7. Check for pinched or kinked supply and return lines to
hydro-boost. Reposition or replace any damaged lines.
8. Check for damaged brake lines. Replace any damaged
brake lines.
9. Check for malfunctioning hydro-boost. Depress brake
pedal several times, with engine off, to exhaust
accumulator pressure. Depress brake pedal and start
engine.
a. Brake pedal should fall, then push back against opera-
tor's foot.
b. Perform pressure test (Section 8).
c. Replace hydro-boost if not operating properly.
10. Check power steering system. Refer to step 6 in the
Diagnostic portion of Hard Steering in Section 8.
Noisy Brakes
1. Check brake pads for proper installation, contamination,
or distortion. Check brake pads for excessive wear. Mini-
mum brake lining thickness is 1/8 in. (3.2 mm). Replace
brake pads as sets (front or rear) if any pad does not meet
specifications. Make sure pads are flat and smooth.
2. Check rotor for glazing or scoring. Turn the rotor if glazed
or scored. Do not exceed the minimum thickness shown
on the inside of the rotor hat section. It is not
recommended that rotors be turned when spotted or heat
checked.
3. Check halfshaft mounting.
a. Apply a thread-locking compound to the halfshaft and
rotor-to-output flange capscrews, or use bolts with
pre-applied compound, and torque to 57 lb-ft (77
N•m).
b. Apply a thread-locking compound to the halfshaft
retaining capscrew (in geared hub) and torque to
40 lb-ft (54 N•m). Tighten any loose fasteners.
Brake System 7-5