inlet port. Also connect a manifold with an air gauge and
close manual shut-off valve to outlet.
With air control valve in "out" position, open manual
valve to build up 689-861 kPa (100-125 psi) to inlet port.
Shut off manual valve. No air leakage is allowed around
piston or through casting surfaces. Permissible leakage
at exhaust port is a 25 mm (1") soap bubble in six
Push control valve in and build up 689-861 kPa (100-
125 psi) pressure at both inlet and outlet. Shut off
manual manual valve and repeat above leakage test.
Pull control valve out. Outlet port pressure should
exhaust to zero through valve.
Begin with zero pressure at inlet and outlet. Hold
control valve "in" and open manual valve to allow 48-241
kPa (7-35 psi) pressure to build up at both inlet and
outlet. Control of valve should remain "in" at 48-241 kPa
(7-35 psi) and above.
Second check is accomplished with 689-861 kPa
(100-125 psi) in both inlet and outlet ports and both
manual shut-off valves closed. Slowly open manual valve
at outlet to bleed down pressure. The spring brake
control should automatically move "out" when air
pressure at inlet port reaches 48-241 kPa (7-35 psi).
If spring brake control valve does not perform as
described it should be repaired or replaced.
DISASSEMBLY (Fig. 2)
Before moving spring brake control valve from
vehicle, drain all air from all reservoirs.
After valve is removed from vehicle, inspect it for
damage. If casting is broken or shows fractures
replace valve assembly.
Carefully remove end cap snap ring.
End cap, O-ring and spring can be removed
Remove nut, washer and valve assembly.
Pull piston with the knob out end of body and
remove O-ring from piston.
CLEANING AND INSPECTION
Wash all metal parts in cleaning solvent. Inspect
body and end cap seats. Face of seats must be flat and
smooth with no cracks or nicks.
Use new parts supplied in repair kit.
REASSEMBLY (Fig. 2)
Lubricate O-rings, O-ring sealing surfaces and piston-to-
Install O-ring on piston and insert piston into
body, aligning hex on piston to hex on body.
Position valve assembly over end of piston, then
position washer over piston stud end against
metal face of valve.
Install nut and torque as specified on Fig.
Piston should move smoothly back and forth in
Install spring with small end against valve disc.
Position O-ring over end cap. Align end cap over
spring and push end cap into body.
Hold end cap to prevent spring pushing end cap out.
Install snap ring in valve body groove.
Plunger should move in and out by applying force to
move plunger in and releasing it.
SERVICE CHECKS as outlined.
Lubricate O-rings, O-ring sealing surfaces and stem
with Item 3 of LUBRICANT SPECIFICATIONS (refer to
Fig. 4 for numbers in parenthesis).
Install new O-rings on stem (10) and piston (5).
Insert stem in valve body; then position piston (5)
in valve body over stem.
Install stem nut (3).
Install valve end cap (1) and new gasket (2).
Before vehicle is returned to service, perform SERVICE
CHECKS on valve as outlined.
TWO WAY CONTROL VALVE (BENDIX TYPE TW-1)
The TW-1 two-way control valve, which is an off-on
valve, is mounted on the instrument panel and is
primarily used in conjunction with various other air
devices in vehicle air systems. The systems in which
these valves may be used are: transmission air control
valve, quick release valve, two-speed shift cylinders,
manually operated tractor protection valve and power
divider lock-out system.
CTS-4079 - CHAPTER VII - Page 4