Bus Air Suspension sinking on one side.

[NigelNZ]

Odd situation where the suspension works when driving but then sags when parked. Now that it is parked it is not going up again but if driven it will go up. Can you figure what the problem is from these symptoms?
It is an old Mercedes bus, I have just purchased.....runs smoothly and air bags relatively new I am told.

[Ray,IN]

When was the air dryer filter last replaced? When it is not working as designed, many compressed air system maladies can occur.

[DRM901]

Are the air tanks holding pressure? Is the air dryer purging when you first start it up, and not continuing to do so after that?

It sounds like the engine needs to be at a higher RPM to build enough pressure for the system.

The sags when parked sounds like a leak - in the air bags, a check valve, or a line. The air is going somewhere.

[NigelNZ]

Originally Posted by DRM901

Are the air tanks holding pressure? Is the air dryer purging when you first start it up, and not continuing to do so after that?

It sounds like the engine needs to be at a higher RPM to build enough pressure for the system.

The sags when parked sounds like a leak - in the air bags, a check valve, or a line. The air is going somewhere.

I tried higher revs but nope....that didn't solve it. Probably a valve or leak. Thanks.

[Turbojack]

Going by guess of your system. There are going to be ride height valves. My guess is one each side of rear and either one or two on the front. These keep the bus up as long as bus is running and the air compressor on the moto is suppling air for the brakes and the air bags. I could be that the ride height valves are leaking and releasing the air in the bags. You did not say if only one side or both sides.

[NigelNZ]

Originally Posted by Turbojack

Going by guess of your system. There are going to be ride height valves. My guess is one each side of rear and either one or two on the front. These keep the bus up as long as bus is running and the air compressor on the moto is suppling air for the brakes and the air bags. I could be that the ride height valves are leaking and releasing the air in the bags. You did not say if only one side or both sides.

It is sagging on the rear right side only. The motor is a diesel Mercedes Benz, a 1977 model bus. The motor is in good condition and runs like a dream. I am new to all this so FINDING the said valves will be an interesting exercise
Any clues for example what they even would look like! I haven't spent much time looking yet.
Any help much appreciated. Yeh, the valve could easily be clogged with dust and so jamming partially open......I hope it is something as simple as that.

[vito.a]

Air suspensions need periodic maintenance. Use a bottle of soapy water to find the leaks and fix them. Most of the time you can remove the small plastic air tubing and snip 1/4" off the end and reinsert it to stop the leak.

Before you start, make up some 2x8 boards stacked onto each other and screwed together. Drive up on them to give yourself clearance.

[Ray,IN]

Before crawling underneath your bus do as vito said, make ramps tall enough for you to get underneath when the air springs are deflated. Otherwise there is a possibility of squashing yourself. About 5 years ago an RV technician in N. Indiana ignored this, the MH he was under lost air pressure, pinning him underneath and he suffocated before co-workers found him.
The ride height valves are similar to this in appearance. Of Course yours will be black and dirty. There should be 3 of them.
You need a bright light and a bottle of soapy water to locate air leake, I use kids bubble soap instead because it make more and larger bubbles.
I suspect that air spring has a leak in the air bladder; that's where I'd begin.

[NigelNZ]

Thanks......I am waiting for my friend to help me jack it up. Today I cleaned up some of the engine just to get a bit more familiar with what I was looking at. The engine has been cared for well and just had a heavy coating of dust....but wow......quite a complex of pipes and so forth!
Thanks for those pictures, it all helps.
We have a hurricane just closing in so weather will be crap for a few days I guess and then hopefully my friend will be back to help me. And yes, I got it on the being careful.....I don't want to be squashed like a bug!

Originally Posted by Ray,IN

Before crawling underneath your bus do as vito said, make ramps tall enough for you to get underneath when the air springs are deflated. Otherwise there is a possibility of squashing yourself. About 5 years ago an RV technician in N. Indiana ignored this, the MH he was under lost air pressure, pinning him underneath and he suffocated before co-workers found him.
The ride height valves are similar to this in appearance. Of Course yours will be black and dirty. There should be 3 of them.
You need a bright light and a bottle of soapy water to locate air leake, I use kids bubble soap instead because it make more and larger bubbles.
I suspect that air spring has a leak in the air bladder; that's where I'd begin.

[NigelNZ]

This is a photo taken today from the bottom looking up. This is where the air is escaping from. Is it a valve? It is located at the front of the bus near the drivers seat underneath. The air was coming out that little hole in the center.

[Turbojack]

Can you get a picture from the side?

[NigelNZ]

Yes I will try, Thanks