Chevrolet 70 1969 Series, Shop Manual

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BRAKES 5B-70
STOPMASTER TROUBLESHOOTING CHART
"F A IL - S A F E ” PARKING BR AKE W I L L N O T R E L E A S E
PROBABLE C A U SE
R E M E D Y
1
.
Air leak in "Fail-Safe” lines
1
.
Check air system and correct leaks
2. Loose clamp ring or cap 2. Tighten and check for air leaks
3. Leakage at release bolt
3. Replace piston and seal assembly
4. Faulty piston O-ring seal 4. Replace piston O-ring seal
5. Foreign material in "Fail-Safe" chamber 5. Cl'ean with solvent and lubricate
6. Improper wedge adjustment 6. Make wedge adjustment
7. Corroded "Fail-Safe" spring 7. Replace cap and spring assembly
"F A IL - S A F E " PARKING BR AKE W I L L N O T APPLY
PROBABLE CA U SE
1. "Fail-Safe" spring not fully released
2. Inoperative parking brake control valve or
quick release valve
3. Foreign material in chambers or piston stuck
in cap
4. "Fail-Safe" spring failure
5. Rollers not aligned with plungers or wedge not
mated with diaphragm plate rod
6. Brakes out of adjustment
R E M E D Y
1. Turn release bolt counterclockwise
2. Check operation of valves as outlined in
Maintenance Manual and replace if necessary
3. Disassemble and clean with solvent; lubricate
piston and cap
4. Replace cap and spring assembly
5. Remove non-pressure housing and check
installation of wedge
6. Adjust brakes; check operation of automatic
adjusters
A U T O M A T IC A D JU S T E R S IN O PE R A T IV E
R E M E D Y
PROBABLE CA U SE
1. Guide installed backwards 1. Remove plunger guide components and
reassemble
2. Guide spring missing or weak
2. Replace guide spring
3. Plunger seal failure
3. Replace seal; clean and lubricate actuation
parts
4. Adjusting bolt threaded into actuator too tight
4, Back off bolt 1/4 turn
5. Plunger guide washer omitted
5. Replace washer
CHEVROLET SERIES 70-80 HEAVY DUTY TRUCK SHO P M ANUAL