BRAKES 5-72
STOPMASTER TROUBLESHOOTING CHART
"FAIL-SAFE" PARKING BRAKE WILL NOT RELEASE
REMEDY
PROBABLE CAUSE
1. Air leak in "F ail-Safe" lin e s
2. L oose clam p ring or cap
3. Leakage at r e le a s e bolt
4. Faulty piston O -ring sea l
5. Foreign m aterial in "Fail-Safe" cham ber
6
. Improper w edge adjustment
7. Corroded "F ail-Safe" spring
1. Check air sy stem and c o r r e ct leaks
2. Tighten and check for air leaks
3. R eplace piston and se a l assem b ly
4. R eplace piston O -ring se a l
5. Clean with solvent and lubricate
6
. Make wedge adjustment
7. Replace cap and spring assem b ly
"FAIL-SAFE" PARKING BRAKE WILL NOT APPLY
REMEDY
PROBABLE CAUSE
1. "F ail-Safe" spring not fully r e lea sed
2. Inoperative parking brake control valve or
quick r e le a s e valve
3. Foreign m aterial in cham bers or piston stuck
in cap
4. " F a il-S a fe” spring failure
5. R o lle r s not aligned with plungers or wedge not
mated with diaphragm plate rod
6
. Brakes out of adjustment
1. Turn r e le a s e bolt counterclockw ise
2. Check operation of va lv es as outlined in
Maintenance Manual and rep lace if n e c e ssa r y
3. D isa ssem b le and clean with solvent; lubricate
piston and cap
4. R eplace cap and spring assem b ly
5. Rem ove n o n -p ressu re housing and check
in stallation of wedge
6
. Adjust brakes; check operation of automatic
adjusters
AUTOMATIC ADJUSTERS INOPERATIVE
REMEDY
PROBABLE CAUSE
1. Guide in sta lled backwards
2. Guide spring m issin g or weak
3. Plunger se a l failure
4 . Adjusting bolt threaded into actuator too tight
5. Plunger guide w asher om itted
1. Rem ove plunger guide com ponents and
re a ssem b le
2. R eplace guide spring
3. Replace seal; clean and lubricate actuation
parts
4. Back off bolt 1 / 4 turn
5. Replace w asher
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCK SHOP MANUAL
Summary of Contents for 70 Series 1970
Page 1: ...CHEVROLET HEAVY DUTY TRUCK SERVICE MANUAL...
Page 9: ...LUBRICATION 0 2 CHEVROLET SERIES 70 90 HEAVY DUTY TRUCK SHOP MANUAL...
Page 11: ...LUBRICATION 0 4 CHEVROLET SERIES 70 90 HEAVY DUTY TRUCK SHOP MANUAL...
Page 13: ...LUBRICATION 0 6 CHEVROLET SERIES 70 90 HEAVY DUTY TRUCK SHOP MANUAL...
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