Strange Air Leak ....I seek Your Collective wisdom :)

[Eric]

Ok 1st thing 1st The Bus : 1985 Neoplan AN440,6v92TA, Allison 730..

When Idling I can only build around 90-100 psi there is a strange device located dead center of the front wheels that has 3 lines and an opening that appears to be for releasing air constantly blowing out my precious Air. When driving it builds all the way till 125psi and everything is normal. Here's the kicker this device will abrubtly WHOOSH all the air from the passenger air bag as soon as you turn off  the bus! The first time it happened I thought the tire blew! within 5 minutes it will drain every last PSI from the rig! Not sure what it is but i have accomplished tapping on it with a hammer a few times the bugger is nearly impossible to get too it seems! Any helped REALLY appreciated!

[Len Silva]

Only a guess 'cause I don't know your bus, but it sounds like the kneeling circuit. The fact that it seems related to the door is a clue.

[HighTechRedneck]

I agree it sounds like the kneeling system.  Another clue is how fast it dumps the air.

[Buffalo SpaceShip]

I think they're on the right track.  Block up your bus, work with a portable compressor, and try to bypass the circuit.  It might just take a couple of iron pipe fitting plugs.  Do you have an airline schematic of your bus?

HTH,
Brian Brown

[Tony LEE]

"within 5 minutes it will drain every last PSI from the rig!"

This shouldn't happen with a kneeling circuit. Drain the airbag to kneel, but not all the rest.

(Does that bus have an air dryer same as MCI)

[Eric]

Well I don't have ANY info for the bus and I don't think it has the kneel function..and i would love to take it apart but i can't seem to get to it!!! I'll post some pictures today!

[buswarrior]

If the pressure protection valves are failed/removed/bypassed, a failed kneeler will most certainly EMPTY the air system as described.

As will a blown suspension bellow in every other busnut's coach.

There is no regularly performed inspection procedure/test for the pressure protection valves, and one might be very scared to find out how some wrenches might pretend to tell you how if asked....

To test the PPV, you must induce an air loss in the aux circuits and confirm that the PPV stops the air loss, protecting the brake circuit tanks, at a pressure that is equal to or higher than the manufacturer's spec. Opening the drain on your aux tank is an easy way to make a "leak".

The PPV are cheap to buy and may be considered a consumable.

happy coaching!
buswarrior