Hummer H1 Service Manual page 468

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REAR CALIPER OVERHAUL
Rear Caliper Disassembly (Figure 7-37)
1. Mount caliper in vise so parking brake lever and spring are
facing upward.
2. Unseat and remove parking brake lever spring. Use large slip
joint pliers.
3. Remove bolt that secures lever retainer to thrust screw.
Then remove retainer, but do not remove parking brake
lever at this time.
4. Remove caliper piston as follows:
a. Remove piston retaining screw with hex key and pencil
magnet. Use magnet to withdraw screw after loosening
it.
b. Extend piston by rotating parking brake lever.
c. Rotate caliper piston in counter-clockwise direction un-
til it comes off thrust screw. Rotate piston by hand, or
use piston retraction tool J-42553 (Figure 7-36).
DISC BRAKE
PISTON
RETRACTION
TOOL
J-42553
Figure 7-36: Piston Removal
d. Pull piston out of dust boot and remove it from caliper.
5. Remove piston dust boot with pry tool.
CAUTION: Exercise care when removing the boot. Do not al-
low the pry tool to scratch the caliper piston bore.
6. Remove thrust screw retaining ring. Carefully unseat ring
with long, thin, flat blade screwdriver. Apply single wrap
of electrical tape around screwdriver blade to avoid
scratching bore, or thrust screw spring shield.
7. Grasp thrust screw and slide screw, shield, and spring out
of bore as assembly. Rotate brake lever to assist removal.
8. Remove parking brake lever from actuator shaft.
9. Remove actuator shaft bearing balls with pencil magnet.
10. Remove thrust screw centering pin plug and spacer. Then
reach inside caliper piston bore and push centering pin out
of caliper with finger pressure.
11. Push bearing plate and actuator shaft out of caliper bore
using finger pressure.
12. Remove caliper piston seal from groove in piston bore.
Use wood pencil to remove seal. Do not use metal tools
that will scratch bore.
05745159
CALIPER
PISTON
13. Remove and discard actuator shaft dust seal. Discard seal.
14. Remove and discard centering pin plug O-ring.
15. Remove and discard centering pin O-ring.
16. Remove O-ring from actuator shaft. Then remove thrust
bearing and race from shaft. Discard O-ring but retain
bearing and race if in good condition.
17. Disassembly caliper piston as follows:
a. Remove retaining ring with internal type ring pliers.
b. Remove wave washer.
c. Remove thrust washer and bearing.
d. Remove cone clutch.
Caliper Cleaning and Inspection
Clean the caliper parts in standard parts cleaning solvent, or
denatured alcohol. Dry the parts with compressed air or lint
free shop towels.
Replace the caliper piston if corroded, rusted, or scored. Do not
attempt to salvage any piston where rust or scoring has broken
through the piston plating. Also, do not use any type of abra-
sive material on the piston surface. This practice will damage
the plating and cause the piston to stick or seize in the bore.
Check condition of the caliper piston bore. Moderate surface
discoloration is normal and not a cause for replacement. How-
ever, the caliper should be replaced if the bore is corroded, pit-
ted, or scored. The bore can be lightly polished with crocus
cloth but must not be honed or sanded.
Inspect the thrust screw and actuator shaft parts. Replace the
thrust screw, spring shield, and retaining ring if damaged, or
distorted. Replace the actuator shaft, bearing plate, and bearing
balls if scored, cracked, worn, corroded, or pitted. Also replace
the shaft bearing and race as a set if either part is worn, rough,
pitted, or scored.
Replace the caliper piston cone clutch, bearing and race, or
wave washer if worn, scored, or damaged.
Assembly (Figure 7-37)
1. Install new actuator shaft dust seal in caliper. Use one-inch
socket to seat seal in housing. The open portion of seal
metal retainer faces out. Lubricate seal lip with DOT 3
brake fluid afterward.
2. Lubricate actuator shaft, bearings, race, and plate with
DOT 3 brake fluid. Then install thrust bearing and race on
shaft and secure with new O-ring.
3. Install actuator shaft in caliper. Then install plastic bearing
plate and the three ball bearings.
4. Install new O-ring on thrust screw centering pin and install
pin in caliper. Position pin so blade will align with slot in
thrust screw.
5. Lubricate thrust screw with DOT 3 brake fluid. Then install
spring and retaining ring on thrust screw.
Brake System 7-29