TRUCK SERVICE MANUAL
QUICK RELEASE VALVE, LIMITING AND QUICK RELEASE VALVE COMBINATION
Fig. 1. Quick Release Valve
QUICK RELEASE VALVE
edges of the diaphragm will seal against the cover seat.
The exhaust port is still sealed by the center portion of
the diaphragm. When the brake valve is released, air
pressure above the diaphragm is exhausted, allowing the
The purpose of the quick release valve is to reduce
diaphragm to raise, opening the exhaust port and
the time required to release the brakes by hastening the
allowing brake chamber pressure to release.
exhaust of air pressure from the brake chambers. When
a brake valve application is released, the exhaust of the
quick release valve opens and the air pressure
Every year or 100, 000 miles remove the quick
accumulated in the brake chamber is exhausted through
release valve, dismantle it and clean all parts.
the quick release valve, rather hastening than exhausting
back through the brake valve .
The quick release valve opens amounted on the
frame close to the brake chambers it controls. The line
connected through to the quick release port is the
delivery line from the brake valve. The two side ports are
the brake chamber connections, and the bottom port is
Apply the brakes and observe that when the brakes
are released, air pressure is quickly exhausted through
the exhaust port of the valve. Be sure the exhaust port is
NOTE: In some special applications a
not restricted in any way.
spring and spring seat will be found in
quick release valves.
The valve must be tested at regular intervals for
leakage using Leak Detector Tester (SE-2326) at
exhaust port with the brakes applied. On releasing the
When a brake valve application is made air pressure
brakes see that the valve releases immediately with the
enters the top (brake valve) port of the QR-1 valve,
corresponding return movement of the foot pedal.
moves the diaphragm down and flows into the brake
Leakage may be caused by dirt in the valve or a
defective diaphragm. Leakage in excess of a 1" soap
bubble in 1 second is not permissible. If excessive
As soon as the brake chamber pressure beneath the
leakage is found, the relay valve must be repaired or
diaphragm equals the air pressure being delivered in the
brake valve, the outer