Hi, the writing on this Bendix valve would say ' use pin to drain manually'
This valve is fitted to the base of the air dryer reciever cannister and is there to automatically drain waste moisture collected from the air taken in by the compressor when the engine is running. Water is undesirable in the brake system as it can impede operation and freeze in the winter also, aswell as reducing the capacity of the air tanks to hold air.
A test of this valves operation would be to run the engine untill the air is built fully, Secure the park brake and stop the engine, remove the keys for safety.
Use a soap / water filled sqeezy bottle to sudds up the underside central pin orifice. Get someone to apply the service (foot)brake several times, once sufficient pressure has been reduced in the lorrys brake system, the drainer should only then eject air/water waste out through the central hole for a brief period of a couple sec's, then stop ejecting automatically. about 4-5 applications of brake should be ample.
This test ensures the auto drain valve works and reseals.
You did not say if it dribbles constantly, if so a new one can be purchased from a commercial vehicle factor parts supplier. Once you run the engine, as the air is building it should not be leeking , only when you are 'using air'(using air suspension/park brake/service brake).
If there is lots of black oil coming from the port, then you probably have compressor issues and further examination from a trained HGV technician should be the next port of call.
The valve should not constantly leak, if it does, you may have other air leaks in the system which are causing a 'pressure drop', allowing the valve to vent, should be corrected first, and then change the drainer valve, (but only if it constantly leaks though)
hope this helps
zomerzet, September 2011
