5-4
F-916-0217 Edition
TROUBLESHOOTING GUIDE
Brakes
For maintenance procedures, see
.
PROBLEM
PROBABLE CAUSE
SOLUTION
NO BRAKES OR BRAKES ARE
INTERMITTENT
Brake air system improperly connected
Reconnect hand valves properly.
Relay/Emergency valve plugged
Clean valve.
Defective tractor protection valve
Repair or replace.
Restricted tubing or hose line
Locate and eliminate restriction.
Broken line
Locate break and repair.
Tractor air system failure
Troubleshoot tractor air system and repair.
Check ABS system function.
SINGLE BRAKE DRAGGING OR
LOCKED
Broken internal brake component
Locate and replace broken part
Flat spot on cam roller or cam shaft
Replace and lubricate.
Improper adjustment
Adjust slack adjusters
Spider bushing or cam bracket bushing
binding
Lubricate or replace bushing.
Improper lubrication
Lubricate per
Worn brake shoe bushing
Replace bushing.
Brake drum distortion
Replace drum.
Broken brake chamber spring
Replace spring.
Brake chamber pushrod binding
Re-align brake chamber bracket.
Air brake line loose or broken
Tighten or repair.
UNEVEN BRAKES
See “SINGLE BRAKE DRAGGING OR LOCKED”
Restriction in hose
Locate restriction and remove.
Worn brake linings
Reline brakes.
Grease on linings
Reline brakes.
Broken slack adjuster
Replace slack adjuster
Leaking brake chamber diaphragm
Replace diaphragm.
BRAKES APPLY TOO SLOWLY
Brakes need adjusting or lubrication
Adjust or lubricate as needed.
Low air pressure in brake system (below
105 PSI)
Check tractor air system.
Restricted tubing or hose
Locate restriction and remove.
Defective relay valve
Clean or replace.
Call Factory or see qualified Trailer/Brake Technician
BRAKES RELEASE TOO SLOWLY
Brakes need adjusting or lubrication
Adjust or lubricate as needed.
Brake rigging binding
Align brakes or replace bent parts.
Exhaust port of relay valve restricted or
plugged
Clean valve.
Tractor pressure too low
Adjust to provide 105 psi min.
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