AIR SYSTEM COMPONENTS
SUB-SECTION 9C
OPERATING AND LEAKAGE. TEST To determine the
RELAY VALVE (36Z650)
serviceability of the relay valve, perform the following test:
DESCRIPTION. The relay valve serves to speed up the ap
1. Fully charge the air system and adjust the brakes.
plication ma release of the rear wheel brakes. The valve
operates as a remote controllad brake valve, delivering air
2. Make several brake applications and check for prompt
pressure directly from the reservoir to the brake chambers,
application and release of all rear wheel brakes.
at a rata proportional to the pressure delivered to the front
brake chambers by the treadle valve.
3. With the treadle valve in the released position, check the
exhaust port of the relay valve for inlet valve and valve
The relay valve acts very rapidly because of the small
guide O-ring leakage. This can be done by applying soap
volume of air required between the cover and relay piston
suds to the exhaust valve,
(see Figure 9C-6). When the treadle valve is applied, air
pressure enters this small cavity above the piston through
4. Make and hold a treadle valve, and check the exhaust
the service port and forces the piston down. The exhaust
valve seat moves down with the piston and seats on the
port for leakage. If excessive leakage is detected, the insert
inner or exhaust port of the inlet and exhaust valve, sealing
or exhaust valve only should be replaced. If leakage still
off the exhaust passage. At the same time, the outer or inlet
occurs at the exhaust port, the leakage could be at the relay
part of the inlet and exhaust valve moves off its seat, per-
piston O-ring or possibly at the exhaust valve seat. Continue
mitting air from the dry tank past the open inlet valve to
to hold the brake application and check between the cover
the brake chambers.
and body for cover O-ring leakage.
5. If the valve does not function as described in the above
test, or if leakage is excessive, it is recommendad that the
valve be replaced. If the valve is to be overhauled, contact
the nearest Bendix-Westinghouse distributor for overhaul
information and the necessary parts.
NOTE
The inlet and exhaust valve assembly, generally re-
ferred to as the R-6 insert, can be removed and re-
placed without disturbing the valve mounting or
connecting lines. Contact Bendix-Westinghouse for
information concerning the insert.
Figure 9C-6. Relay Valve (36Z650)
REMOVAL. To remove the relay valve, proceed as follows:
me air pressure being delivered by the open inlet valve is
1. Block and hold the vehicle with wheel chocks.
also impressed on the bottom area of the relay piston.
When this pressure beneath the piston approaches that
2. Open the drain cock on each reservoir to drain the pres-
king delivered above, the piston spring lifts the piston
sure from the air system.
slightly and the inlet valve spring returns the inlet valve to
its seat. The exhaust remains closed as the service line pres-
3. Disconnect the air lines attached to the relay valve.
sure balances the delivery pressure,
4. Remove the valve mounting bolts and remove the valve.
When the deliverad pressure is raised, lowered or com-
pletely exhaustad, the valve reacts instantly to these
INSTALLATION. To install a new or rebuilt relay valve,
changes. If the treadle valve is released, the air above the
proceed as follows:
piston is exhausted. The air beneath the piston will then lift
1. Clean and inspect the air lines which connect to the
the piston and the exhaust valve, exposing the exhaust pas-
relay valve. Replace any air lines which are damaged.
sage to atmosphere. With the exhaust passage open, the air
pressure in the brake chamber is vented through the relay
2. Mount the relay valve securely with the mounting bolts.
valve, ad the brakes release.
9C-7
