SUB-SECTION SC
AIR SYSTEM COMPONENTS
pressure at this port moves the diaphragm down and closes
REMOVAL. To remove the treadle valve, proceed as
the exhaust port. At the same time, this air pressure forces
follows:
the edges of the diaphragm down, and air flows by the
diaphragm to the brake chambers.
1. Block and hold the vehicle by some means other than
the carrier brakes.
As soon as the brake chamber pressure beneath the dia-
phragm equals the air pressure being delivered to the valve,
2. Open the drain cock on each reservoir to exhaust air
the outer edge of the diaphragm will seal against the cover
pressure from the air system.
seat. The exhaust port remains sealed by the center portion
of the diaphragm. When the treadle valve is released, air pres-
3. Disconnect the air lines attached to the treadle valve.
sure above the diaphragm is exhausted, allowing the dia-
Remove the mounting bolts. Then remove the treadle valve.
phragm to raise, opening the exhaust port and allowing
brake chamber pressure to exhaust through the quick re-
INSTALLATION. To install a new or rebuilt treadle valve,
lease valve.
proceed as follows:
OPERATING TEST. Make a treadle valve application and
1. Clean the air line to the treadle.
note that the brake chambers served by the quick release
valve apply the brakes. Release the application and observe
2. Mount the treadle valve on the cab floor and install the
that the air pressure is quickly exhausted through the ex-
mounting bolts.
haust port of the quick release valve.
3. Connect the air line to the valve and plug any unused
LEAKAGE TEST. Make and hold a treadle valve applica-
ports.
tion, and then check the exhaust port of the quick release
valve for leakage. If the valve does not function as just
4. Test the valve for serviceability by performing the
described, or leaks excessively, it is recommended that the
Operating and Leakage Tests.
valve be replaced. If overhaul information is required, con-
tact the nearest Bendix-Westinghouse distributor.
QUICK RELEASE VALVE (38Z254)
REMOVAL. To remove the quick release valve, proceed as
DESCRIPTION. The quick release valve speeds up the re-
follows:
lease of air pressure from the brake chambers. The opera-
tion of the quick release valve is as follows (see figure
1. Block or hold the vehicle in position with wheel chocks.
9C-4):
2. Open the drain cocks on each reservoir to drain the air
pressure from the air system.
3. Disconnect the air lines connected to the quick release
valve.
4. Remove the mounting bolts, and then the valve.
INSTALLATION. Install a new or rebuilt quick release
valve as follows:
1. Mount the quick release valve with mounting bolts and
lockwashers with the valve's exhaust port pointing down.
2. Connect the treadle valve line to the top port and the
brake chamber lines to the side ports of the valve.
3. Be sure the exhaust port of the valve is not restricted.
Figure 9C-4. Quick Release Valve (36Z254)
4. Test the valve for serviceability by performing the
When a treadle valve application is made, air pressure enters
Operating and Leakage Tests.
the top (supply) port of the quick release valve, Air
9C-5
