Every 160,000 km (100,000 miles) or every year,
remove, disassemble, clean and inspect all parts. If
signs or wear or deterioration are found, install new
parts. It is recommended all rubber parts be replaced.
SERVICE CHECKS Operation Test
Block vehicle and hold by means other than vehicle
brakes. Charge air brake system to governor cut-out
Place parking control valve in the "apply"
position. Observe that the spring brake actuators
apply promptly. In the delivery port of the
inversion valve install a test gauge known to be
accurate. Place the parking control valve in the
"release" position. Observe that the spring brake
actuators release fully.
With the parking control valve in the "release"
position, note the gauge pressure reading
(should be approximately the same as gauge on
instrument panel). If the pressure reading is
Place the parking control valve in the "apply"
position, the gauge reading should drop to zero
promptly. A slow release of pressure could
indicate faulty operation of the single check valve
(within the Modulating Valve). At approximately
48-241 kpa (7-35 psi) the spring parking brakes
should be fully applied.
Place the parking control valve in the "release"
reservoir and drain it completely.
Apply the foot brake valve several times and
note that the pressure reading on the gauge
decreases each time the foot brake valve is
applied. After the foot brake valve has been
applied several times, pressure on the gauge will
drop to the point where release of the spring
brake actuators will no longer occur.
With air system fully charged and parking brake
control valve in "release" position, use the Leak Detector
Tester around valve cover and exhaust port to detect air
leakage. A slight leakage is permitted.
If inversion valve does not function as described
above or leakage is excessive, it is recommended that
the valve either be replaced or repaired.
Apply parking brakes and drain all air reservoirs.
Mark or identify all air lines before disconnecting
from inversion valve. Then disconnect air lines.
Remove the two mounting bolts from valve and
Install inversion valve using the two mounting
Connect air lines. Make sure they are installed at
the same ports, 3. Before releasing vehicle for
service, perform SERVICE CHECKS as outlined.
DISASSEMBLY (Refer to Fig. 2)
Remove socket head pipe plug at check valve.
Remove check valve spring, spring guide and
Separate exhaust diaphragm from cover.
Remove inlet and exhaust valve assembly.
Remove inlet and exhaust valve cap nut and
separate cap nut O-ring.
Remove valve stop, valve spring and inlet and
lockwashers that secure cover to the body.
Cover is under a spring load and should be held while
removing screws to prevent bodily injury.
Remove cover and three piston springs.
Remove small piston and small and large O-ring,
Remove large piston and large and small O-ring
CTS-4079 - CHAPTER VII - Page 6