Hummer H2. Manual — part 780

Fig. 2: Measuring Rotor Thickness
Courtesy of GENERAL MOTORS CORP.

BRAKE ROTOR SURFACE & WEAR INSPECTION

2004 Hummer H2

2003-04 BRAKES Disc - Hummer

1. If the inboard friction surface of the brake rotor is not accessible, reposition and support the caliper with

the brake pads. See BRAKE PADS under REMOVAL & INSTALLATION.

2. Clean the friction surfaces of the brake rotor with denatured alcohol, or an equivalent approved brake

cleaner.

3. Inspect the friction surfaces of the brake rotor for the following braking surface conditions:

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Heavy rust and/or pitting Light surface rust can be removed with an abrasive disc. Heavy surface
rust and/or pitting must be removed by refinishing the rotor. See BRAKE ROTOR
REFINISHING under OVERHAUL.

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Cracks and/or heat spots.

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Excessive blueing discoloration.

4. If the friction surfaces of the brake rotor exhibit one or more of the braking surface conditions, the rotor

requires refinishing or replacement.

5. Using a micrometer, measure and record the scoring depth of any grooves present on the rotor friction

surfaces. See Fig. 3 .

6. Compare the lowest thickness measurement recorded to the rotor minimum allowable thickness after

refinishing and the rotor discard thickness specifications. See DISC BRAKE SPECIFICATIONS .

7. If the brake rotor scoring depth exceeds the specification, or if an excessive amount of scoring is present,

the rotor requires refinishing or replacement. See BRAKE ROTOR under REMOVAL &
INSTALLATION.

WARNING:

Avoid grinding brake linings, sanding brake linings or cleaning wheel
brake parts with a dry brush or with compressed air, when servicing
wheel brake parts. Some models or aftermarket brake parts may contain
asbestos fibers which can become airborne in dust. Breathing dust with
asbestos fibers may cause serious bodily harm. Use a water-dampened
cloth in order to remove any dust on brake parts. Equipment is available
commercially in order to perform this washing function. These wet
methods prevent fibers from becoming airborne.

2004 Hummer H2

2003-04 BRAKES Disc - Hummer

Fig. 3: Measuring Rotor Runout
Courtesy of GENERAL MOTORS CORP.

BRAKE CALIPER INSPECTION

2004 Hummer H2

2003-04 BRAKES Disc - Hummer

1. Inspect the brake caliper housing for cracks, excess wear, and/or damage. If any of these conditions are

present, the brake caliper requires replacement. See BRAKE CALIPER under REMOVAL &
INSTALLATION.

2. Inspect the caliper piston dust boot seal for cracks, tears, cuts, deterioration and/or improper seating in the

caliper body. See Fig. 4 . If any of these conditions are present, the brake caliper requires overhaul or
replacement.

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For overhaul, see BRAKE CALIPER under OVERHAUL.

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For replacement, see BRAKE CALIPER under REMOVAL & INSTALLATION.

3. Inspect for brake fluid leakage around the caliper piston dust boot seal and on the disc brake pads. If there

is any evidence of brake fluid leakage, the brake caliper requires overhaul or replacement.

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For overhaul, see BRAKE CALIPER under OVERHAUL.

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For replacement, see BRAKE CALIPER under REMOVAL & INSTALLATION.

4. Inspect for smooth and complete travel of the caliper piston, or pistons, into the caliper bore, or bores.

The movement of a caliper piston into a caliper bore should be smooth and even.

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For single piston caliper applications, insert a discarded inner brake pad or block of wood in front
of the piston. Using a large C-clamp installed over the body of the caliper and against the brake pad
or block of wood, slowly bottom the piston in the bore. See Fig. 4 .

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For dual piston caliper applications, insert a discarded inner brake pad or block of wood in front of
the pistons. Using 2 large C-clamps installed over the body of the caliper and against the brake pad
or block of wood, slowly bottom the pistons evenly into the bores.

5. If a caliper piston is frozen or difficult to bottom, the caliper requires overhaul or replacement.

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For overhaul, see BRAKE CALIPER under OVERHAUL.

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For replacement, see BRAKE CALIPER under REMOVAL & INSTALLATION.

WARNING:

Avoid grinding brake linings, sanding brake linings or cleaning wheel
brake parts with a dry brush or with compressed air, when servicing
wheel brake parts. Some models or aftermarket brake parts may contain
asbestos fibers which can become airborne in dust. Breathing dust with
asbestos fibers may cause serious bodily harm. Use a water-dampened
cloth in order to remove any dust on brake parts. Equipment is available
commercially in order to perform this washing function. These wet
methods prevent fibers from becoming airborne.

WARNING:

Brake fluid may irritate eyes and skin. In case of eye contact, rinse
thoroughly with water. In case of skin contact, wash with soap and water.
If ingested, consult a physician immediately.

2004 Hummer H2

2003-04 BRAKES Disc - Hummer