GMC 4000 Series Service Manual page 256

NO BRAKES
PROBABLE CAUSE
1. No air pressure
2. Restricted tubing or hose
3. Defective brake valve
INSUFFICIENT BRAKES
PROBABLE CAUSE
1. Low brake line pressure
2. Too much push rod travel
3. Worn linings or drums
4. Leaking chamber diaphragm
5. Slack adjusters out of adjustment
. Wrong size brake chambers
6
SLOW BRAKE APPLICATION
PROBABLE CAUSE
1. Low brake line pressure
2. Linkage binding
3. Too much push rod travel
4. Restriction in line
5. Leaking brake valve
. Worn linings or drums
6
7. Leaking chamber diaphragm
. Brake shoe anchor pins frozen
8
9. Foot control valve linkage improperly adjusted
10. Camshaft bushings binding or worn
G M C S E R V I C E M A N U A L
GENERAL TROUBLESHOOTING CHART
REMEDY
1. Check for leaks, broken lines, etc. Repair or
replace as necessary
. Replace defective parts.
2
3. Repair or replace
REMEDY
. Check for leaks, etc. and repair
1
. Adjust
2
3. Replace as necessary
4. Replace diaphragm
5. Adjust
. Replace according to "Specifications"
6
REMEDY
1. Check for leaks, etc. and repair
. Lubricate linkage
2
3. Adjust
4. Remove restriction or replace line
5. Repair or replace
. Replace as necessary
6
7. Replace diaphragm
. Free up, replace or lubricate as necessary
8
9. Adjust
. Lubricate or replace
1 0
Sec. 5B
Page 249
AIR BRAKES