4
2. Place the trailer supply valve in the exhaust position;
the spring brakes should be applied, Disconnect the
trailer supply line and soap the hose coupling to check
for leaks. A 1” bubble in 5 seconds is permissible.
3. Reconnect supply hose coupling and push the trailer
supply valve into the charge position. The spring brakes
will release. Shut off the engine leaving the ignition
on and open the drain cock on the trailer service
reservoir. The tractor air system should bleed down
to approximately 45 psi with low pressure indication
occurring at 60 psi. There should be no noticeable drop
in pressure in the spring brake reservoir, and the trailer
service reservoir test gauge should read zero psi. Allow
one minute for the air pressure in the service reservoir
to stabilize after obtaining a zero psi reading on the
test gauge. The trailer spring brakes should remain
released. Soap the trailer service reservoir drain cock
and the exhaust port of the SR-2
™
valve checking for
leaks. A 1” bubble in 3 seconds is permissible.
4. Leaving tractor air system pressure at approximately 45
psi, place the trailer supply valve in the exhaust position.
After making sure the trailer spring brakes are applied,
place the trailer supply valve in the charge position and
the spring brakes should release. The trailer supply
valve and possibly the parking control valve may have
to be held in.
NOTE: If the system functions as described, close the
service reservoir drain cock as a fi nal step in completing
these tests.
5. If the SR-2
™
spring brake valve does not function
as described above or leakage is excessive, repair
the valve or replace it with a genuine Bendix service
replacement valve.
REMOVAL OF VALVE FROM VEHICLE
1. Block the vehicle wheels and drain all air system
reservoirs completely.
2. Disconnect all supply, delivery, and exhaust lines
at the trailer spring brake valve. NOTE: Mark all air
lines and their relation to the spring brake valve for
reconnection.
3. Remove the spring brake valve from the trailer spring
brake reservoir.
REMOVAL AND DISASSEMBLY OF THE PRESSURE
PROTECTIVE PISTON (Reference Fig. 1)
1. Remove the four round head machine screws (16)
which secure the spring retainer (17) to the valve
body.
NOTE: Take caution when removing the spring retainer
as it is spring loaded.
2. Remove the spring (9) and pressure protection piston
assembly (8).
3. Remove the piston o-ring.
NOTE: Do not attempt to remove the retaining ring and
stem from the piston.
REMOVAL AND DISASSEMBLY OF THE CONTROL
PISTON (Reference Fig. 1)
1. Note and mark the position of the control piston cover
(12) on the valve body. Remove the four 1/4” - 20 hex
head cap screws (13) and lock washers which retain
the cover to the body.
2. Remove the cover, control piston assembly (14), and
spring (3) from the valve body.
3. From the control piston remove the three o-rings. (1)
and (2).
4. Remove the reservoir port fi tting (15) from the valve
body.
5. From the reservoir port fi tting remove the o-ring (7).
6. Remove the inlet valve spring (6) and inlet and exhaust
valve (5).
7. If so equipped, (Figure 1) remove the screw (19),
washer (20) and diaphragm (11) from the exhaust
port.
REMOVAL AND DISASSEMBLY OF THE TWO SINGLE
CHECK VALVES
1. Remove the two 3/8” socket head pipe plugs which
retain the two single check valves in the body.
2. Remove the two check valve springs, spring guides
and rubber check valves (10).
CLEANING AND INSPECTION
Wash all metal parts in mineral spirits and dry them.
Inspect all parts for excessive wear or deterioration. Inspect
the valve seats for nicks or burrs. Check the springs for
cracks or corrosion. Replace all rubber parts and any part
not found to be serviceable during inspection, using only
genuine Bendix replacement parts.
ASSEMBLY
Prior to reassembling the SR-2
™
valve lubricate all o-rings,
o-ring grooves, piston bores, and metal to metal moving
surfaces with Bendix silicone lubricant BW-650-M piece
number 291126.
REASSEMBLY OF TWO SINGLE CHECK VALVES (10)
(Figure 1 and 7)
Early revision of the SR-2
™
valve contained single
check valves for the service and spring brake reservoirs
respectively consisting of a rubber valve, spring and spring
guide per Figure 7. Since late 1974 the check valves
have consisted of a sub-assembly pc. no. 288252, which
includes the rubber valve and a revised spring (Figure 8).
If the SR-2
™
valve is being repaired with Maintenance Kit
