AIR SYSTEM
SUB-SECTION 9A
move inward to the applied position automatically when
Depress the brake pedal fully. Test gauge pressure should
the pressure drops below 30 pounds (2.06 BARS). Check
approximately equal dash gauge pressure. Hold the pedal in
the rear brakes to be sure they are in the applied position
several different positions; delivery should vary rapidly in
when the Maxibrake control valve is in the applied position.
accordance with changes in pedal position. Check for quick
application and release of all brakes.
Push in the Emergency Release Valve knob and pull out the
Maxibrake control valve knob. Pressure from the emergency
W ith the engine stopped, reduce air pressure to approxi-
air tank should be transferred to the Maxibrake control
mately 30 pounds (2.06 BARS) by making a series of
valve and the Maxibrakes should release.
brake applications. The Maxibrake control knob should
TROUBLESHOOTING
7. UNEVEN BRAKES
1. INSUFFICIENT BRAKES
Brakes need adjusting. lubricating or relining
Brakes need adjusting, lubricating or relining
Grease on brake lining - reline brakes
Low air pressure in the brake system (below 80 pounds)
Brake shoe release spring or brake chamber release spring
Brake valve delivery pressure below normal
broken
Brake drum out of round
2. BRAKES APPLY TOO SLOWLY
Brake chamber diaphragm leaking
Brakes need adjusting or lubricating
Low air pressure in the brake system (below 80 pounds)
8. AIR PRESSURE WILL NOT RISE TO NORMAL
Brake valve delivery pressure below normal
Defective air gauge (registering incorrectly)
Excessive leakage with brakes applied
Excessive leakage.
Restricted tubing or hose line
Reservoir drain cock open
Cut-out cock improperly left open
Governor out of adjustment
3. BRAKES RELEASE TOO SLOWLY
No clearance at compressor unloading valves
Brakes need adjusting or lubricating
Slipping compressor drive belt
Brake valve not returning to fully released position
Defective compressor
Restricted tubing or hose line
Exhaust port of brake valve or quick release valve re-
9. AIR PRESSURE RISES TO NORMAL TOO SLOWLY
stricted or plugged
Excessive leakage
Defective brake valve or quick release valve
Clogged compressor air strainer
No clearance at compressor unloading valves
4. BRAKES DO NOT APPLY
Engine speed too slow
No air pressure in brake system
Compressor discharge valves leaking
Restricted or broken tubing or hose line
Compressor drive belt slipping
Defective brake valve
Worn compressor
Excessive carbon in compressor cylinder head or dis-
charge line
5. BRAKES DO NOT RELEASE
Brake rigging binding
10. AIR PRESSURE RISES ABOVE NORMAL
Brake valve not in fully released position
Defective air gauge (registering incorrectly)
Defective brake valve
Compressor governor out of adjustment
Restriction in tubing or hose line
Defective compressor governor
Restriction in line between governor and compressor
6. BRAKES GRAB
unloading mechanism
Grease on brake lining - reline brakes
Too much clearance at compressor unloader valves
Brake drum out of round
Unloading valve cavities or unloading passage in com-
pressor cylinder head blocked with carbon
Defective brake valve
Brake rigging binding
Compressor unloading valves stuck closed
9A-3
