TRUCK SERVICE MANUAL
Manual draining can be accomplished by inserting
The inlet valve remains open while pressure
a tool in the exhaust port so that the wire in the port may
ascends in the system until maximum governor cutout
be moved up and held until draining is completed.
pressure is reached. The spring action of valve guide in
sump cavity closes the inlet. The inlet valve and exhaust
The heated automatic drain valve will activate the
valve are now closed (Fig. 11)
heating element when the valve body is warmed to 85
Once each year or every 100,000 miles the
automatic drain valve should be removed, disassembled,
cleaned and lubricated. Parts showing signs of wear or
Special attention should be given to the filter when
the maintenance check is made. The filter must be
clean and should be cleaned or replaced if clogged or
Fig . 11
Under no conditions should valve be installed
without a filter installed in the adapter.
(approximately 2 psi), air pressure in the sump cavity
to be ejected from sump cavity until pressure in sump
cavity drops sufficiently to close the exhaust valve. The
length of time the exhaust valve remains open and the
With system charged, make several foot valve
upon the sump pressure and reservoir pressure drop
applications and note each time an application is made if
that occurs each time air is used from the system.
an exhaust of air occurs at exhaust port of the drain
valve. If no air comes out, push the wire stem. If no air
comes out, the filter is plugged and valve should be
removed and cleaned.
With system charged and pressure stabilized in
system, there should be no leaks at the drain valve
exhaust. A constant slight exhaust of air at the drain
valve exhaust could be caused by excessive leakage in
If the automatic drain valve does not function as
described or if leakage is excessive, it is recommended
that it be removed and repaired or replaced.
1. Block and hold vehicle by means other than air
2. Drain air system.
Fig . 12
3. Disconnect heater wire if valve is so equipped.
4. Remove automatic reservoir drain valve.