Air Leak at Brake (Foot) Valve Exhaust Port with Service and
Parking Brakes Released
Note: For air
to leak at the Exhaust Port of any valve: The valve is bad or;
Tank pressure is getting to the Delivery Port from other components.
Tractor Parking System Components Anti-Compound Valve (if equipped
and depending on plumbing)
Spring Brake Control
Spring Brake Chambers
Brake (Foot) Valve
TRACTOR PROTECTION VALVE TESTS
Supply (red knob on dash). If leak continues, go to Step #6.
If leak stops, go to Step #2.
Disconnect Glad Hands and connect to holder on tractor.
Push Trailer Supply. If exhaust Port of Foot Valve leaks, replace
Tractor Protection Valve.
If Exhaust Port of Foot Valve does not leak, problem is in Trailer.
Go to Step #3.
Release Trailer Brakes.
Disconnect Control Line from Service Port of Relay. If leak continues,
go to Step #4.
If leak stops, go to Step #5.
Disconnect Anti-Compound Line (if equipped).
Leak at Exhaust Port of Foot Valve should stop. Replace Trailer
Spring Brake Valve.
Disconnect Delivery Lines to Service Side of Spring Brake Chamber,
one at a time. If there is a leak out of the Service Side of
Chamber, replace Spring Brake Chamber.
With all Delivery Lines disconnected and leak continues, replace
SYSTEM COMPONENT TESTS
1. Pull Park
Control. If leak continues, go to Step #9.
If leak stops, go to Step #7.
Disconnect Anti-Compound Line. If leak stops, replace Anti-Compound
If leak continues, go to Step #8.
If not equipped with Spring Brake Control Valve, go to Step #9.
CONTROL VALVE TEST
Line from Secondary Signal Line. If leak stops, replace Spring
Brake Control Valve.
If leak continues, go to Step #9.
Line to Service Side of Spring Brake Chambers, one at a time.
If there is a leak out of the Service side of the Spring Brake
Chamber, replace Spring Brake Chamber (Remember, there may be
more than one bad chamber).
Steps #1 through #9 and leak continues, disconnect all Delivery
Lines. If leak continues, replace Brake (Foot) valve.
If leak stops, recheck Steps #1 through #9.
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