SLIGHT AIR LEAK THROUGH EXHAUST PORT
Note: A slight air leak, as referenced here, can be identifi ed by holding your hand over the
exhaust port (bottom of the valve box assembly) and detecting a slow build up of pressure
A slight leak through the exhaust port can come from one of two places.
1. Feeding back from the tires through the valve cartridge seat and out the exhaust port. This
would allow a pressure drop in the tire circuit when parking overnight. You would notice a
decrease in tire pressure on the cab controller. (e.g. 90 psi when parking decreases to 75
psi when starting)
2. Through the solenoids mounted on the valve. This would allow supply air (from protection
valve/wet tank) to vent through the solenoids into the same exhaust port. Normally when
the solenoids are in neutral they are seated and prevent any air fl ow through their seat. A
leak here would not drop tire pressures, but would allow the wet tank pressure to drop,
but only to the closing pressure of the pressure protection valve setting of approx. 95 -100
psi.
The source of the leak can be determined by pulling ONLY the exhaust manifold off the valve as-
sembly and determining which valve (steer, drive or trailer) is leaking. The system can still be aired
up and operated with this manifold removed.
To remove the exhaust manifold, fi rst remove the exhaust port elbow from the bottom of the
box. Next remove the two bolts (also at bottom of box) holding the manifold in the box.
Now remove the bolts holding the manifold to the valve assembly (inside the box).
Once it is determined which valve(s) are leaking (indicated by the passage of air out of the ex-
haust port in the valve body), perform the following procedures:
Close all the wheel valves, shut the truck off once it has reached the unloading pressure of the
compressor (e.g. 125 psi) and disconnect the ¼” air line from the side of the valve that is leaking.
This ensures there is no pressure on the tire side of the valve. If the leak stops you have a faulty
valve cartridge as mentioned in #1 above and will have to rebuild the valve. (See “VALVE
REBUILD PROCEDURE” at the back of this manual). If the leak still persists, it is coming through
the solenoids as mentioned in #2 above. The solenoids are equipped with the manual overrides
(either a small blue lever or a recessed push button on solenoid). Activate one then the other a
few times and confi rm if the leak stops. Do one at a time to determine the faulty one. (Each valve
has two solenoids)
NOTE: ENSURE THE TRUCK SUPPLY AIR PRESSURE STAYS ABOVE 95 PSI. IF THE WET
TANK DROPS TO 95 PSI THE PROTECTION VALVE WILL CLOSE AND THEN THERE WILL
NO LONGER BE ANY SUPPLY AIR PRESSURE TO THE SOLENOIDS AND THAT WOULD
ALSO STOP ANY LEAKAGE OUT THE EXHAUST. ALSO KEEP IN MIND THE TRUCK AIR
GAUGES ARE ON THE SERVICE TANKS AND NOT ON THE WET TANK, SO THE WET TANK
COULD DROP TO 90 PSI AND THE TRUCK GAUGES WILL STILL READ SOMETHING HIGH-
ER E.G. 120 PSI.
SERVICE MANUAL
TIREBOSS
TM
Tire Pressure Control
3-13
f:tec\manuals\Service\SERVICEv5.indd - V6-0615
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