Air Bag Replacement

[dale farley]

I brought my bus home today to do some maintenance. As I had discussed in a previous thread, I had a significant leak in my right tag axle air bag. It took about 1/1/2 hour to replace it, because I wasn't really sure about the procedure. But I got it done and everything seems to be fine with the installation.

The bus still drops on the right side when I turn it off. Before removing the tag wheel, I placed 4" of plywood under all 4 of the drive wheels, so it would be off the ground a little. I then placed 2 jacks under the right side and jacked it up enough to make sure the bus wouldn't come down too low with me under it when I drained all the air. Every time I turn off the bus, I hear what sounds like air traveling through a pipe. It is very audible in the area where the front drive air bag and ride height valve are located (see attached picture). I have checked every fitting with soap, my ultrasonic leak detector and a hose (cheap stethoscope), and I can't find a leak. As the bus drops on that side, the noise subsides.

Now that I am out from under the bus, I am wondering if this could be caused by the fact that I still have the right side of the bus jacked up a little bit? The wheels are not off the ground, but it is sitting on the jacks. Could the ride heigth valve be trying to level the right side or does that valve even work when the bus is shut off?

I would go back out and let the jacks down, but it is dark and cold, and I have to jack the bus up again Monday so I can change the Air Dryer cartridge. Sorry for the long post.

[Orren Zook]

Roadrunner,

The leveling valve you show in the picture is mechanical, and would continue to seek level even when the ignition is turned off. If so, check the little hose at the top of the valve (there should be three ports on the side where the leveling arm is) to see if it is exhausting air when you hear the sound described. You've got a couple of variables too, 4" of wood under the drive axle and the right side of the coach jacked up, both of which should cause the leveling valves to operate seeking to level the bus.

Make sure you watch for pinch points while you're under the coach checking this.

[dalej]

Dale if you start jacking on the bus you will let old air out of the valves but new air won't replace it until
the key is in the on position. As you can see in the photo the leveling valve goes through a solenoid that
is run off the 24v, so the key has to be on. Hope this helps....we have this thread somewhere on this site.

[Joe Cannarozzi]

Roadrunner, sounds like that is exactly what is going on. When that ride-height valve begins to function 2 things happen. First there is a delay built in. Second it will adjust very long and slowly. As previously suggested you'll feel the air coming out the exhaust port, a short small tube hooked up to nothing.

[Jon Wehrenberg]

Roadrunner....sorry to disagree with our fine associates, but the ride height valve that was pictured WILL NOT FUNCTION WITH THE KEY OFF.

I have emphasized this before but it needs repeating. Each converter has their own way of handling the leveling of our coaches so we cannot get too specific here, however I have never seen or heard of any Prevost with a level low system that had functioning RIDE HEIGHT valves with the key off.

We can get into a discussion of the general procedures for isolating a leak that allows a coach to lean, but first I wanted to correct the misconception.

However....if that valve leaks it is possible for the coach to lean. If it is leaking the air will escape from the six inch plastic exhaust tube as Joe points out. He also point out about the time delay so be very careful before you put yourself in harms way to insure the coach cannot drop no matter what happens.

[Jon Wehrenberg]

Dale you are correct but if you look closely at the photo I think it is a Norgren valve controlling the air supply to the ride height valve. Depending on the converter it might be pneumatic.