GMC 4000 Series Service Manual page 257

Sec. 5B
Page 250
AIR BRAKES
SLOW BRAKE RELEASE
PROBABLE CAUSE
1. Linkage binding
2. Restriction in line
3. Too much push rod travel
4. Improper seating of valves in application
valve.
5. Binding cam or camshafts
. Weak shoe return springs
6
GRABBING BRAKES
PROBABLE CAUSE
1.
G rea se or dirt on lin in g
2. Brake drum out-of-round
3. Defective application valve
UNEVEN BRAKES
PROBABLE CAUSE
1. Uneven slack adjuster settings
2. Linkage binding at one or more wheels
3. Linings worn uneven
4. Brake shoe return spring weak or broken
5. Defective brake chamber
. Defective brake drum
6
7. Unequal springs in brake chambers or between
brake shoes
SLOW PRESSURE BUILDUP IN RESERVOIRS
PROBABLE CAUSE
1. Clogged air cleaner
.2. Air leak
3. Faulty com pressor
4. Open or leaking reservoir drain cocks.
5. Defective com pressor governor
G M C S E R V I C E M A N U A L
1. Lubricate linkage
. Remove restriction or replace line.
2
3. Adjust
4. Repair or replace
5. Lubricate if possible; replace if not effective.
. Replace springs
6
.
1
. Turn or replace
2
3. Repair or replace
. Adjust properly
1
. Lubricate as necessary
2
3. Adjust or replace
4. Replace
5. Repair or replace
. Repair or replace
6
7. Replace in pairs.
. Clean or replace
1
. Find and repair
2
3. Repair (see
4. Close, repair or replace.
5. Repair or replace
REMEDY
REMEDY
C lean or re lin e .
REMEDY
REMEDY
" Air Compressor" section in
this manual)