Ron W

I have had minor ride height issues in the past, but they just got worse. After parking the car, it started to drop on the left rear, sometimes it would stay level, and sometimes drop. I would cure this by raising and lowering car three times. Each time I lower it, the left side would get higher, by the third time it would be at the correct height. That would last for a couple of months. Then it would repeat, and so would I. Now it's doing it on both sides and doesn't want to go back up. It will stay down all of the time. Even after starting car and driving a while, it stays down. When I raise and lower the car three times, it will stay up and not go down when shut off. Then after I drive to the store and come back it drops again. When I shut off the car and get out, I watch it slowly drop. Takes about 3 minutes to drop. I checked the bags and lines with soap and water. No leaks. I just replaced the control valve unit to see if that was the issue. It didn't cure the issue. If I raise the car, and leave it up, and shut the car off, it stays up, even after driving the car and parking it, it stays up. There are no suspension codes present or past. Any suggestions.

DennisG01

Best guess... the leak in the bags is just at a place you can't see with the soapy water or you didn't spray it well enough or get your head in there far enough to see it. Bags having a small leak (at certain heights/folds) is, by far, the most common culprit. Continuing to drive the car like you have been doing is only going to wear out the compressor prematurely.

Max Blast

As stated, you have a leaky bag.
start replacing both rears as that’s is where you say it starts sagging.

Ron W

Thanks for the input, but the rear air bags were replaced about three years ago and they aren't dry rotted. I also checked the lines and reservoir. So I believe I need to try something else. Any other suggestions would be appreciated.

Max Blast

ah, three years for an aftermarket rear bag sounds about right. Sure they’re not dry rotted but the may be holed from use or a rock lodged in there. These are consumables and owners must treat them as such.

edit: did you say you replaced the valve block? If you’ve been driving around like this for months then your compressor is probably also in need of replacement.

Good news tho: if the rear bags you replaced were arnott and you bought them they’ll replace them for free. Also, compressor replacement is very easy. You don’t even have to jack the car up.

Ron W

Yes, the compressor is not up to spec. only 15.8 bar, so its getting replaced. I will take apart today to see if I can rebuild it first.

DennisG01

Being three years old absolutely doesn't mean they're not the culprit. Don't assume. Check them out better, first. They are the #1 reason for dropping, regardless of years/mileage on them.

Ron W

I had no luck on the pump, so I ordered a new pump and bags. I'll let you know how it turns out. Should receive parts around Wednesday or Thursday, so that's what I'll be doing Thursday night.

bapdco

I've had similar issues lately and just replaced the LF bag. Two weeks later I get lowering on the LF and LR when parked overnight. Just came back from the shop. They checked the bags, compressor, all line, all valves, etc. and can't find anything wrong. ????

Max Blast

.

91stealthes

3-years doesn't matter. I had new bags put up front via Mercedes and 1 was just replaced again in less than 4-months for a pinhole leak

Pmanc

Probably need new air struts I went with bilstein

Ron W

To bapdco, Yeah. I hear that. I went all over this suspension and didn't find a problem before. To continue, I installed new compressor, filter and rear bags. Guess what happened, it still goes down once I shut the engine off. I may have to replace or reprogram the suspension ecm. I reprogram first. Still actively working on it. At least now the compressor doesn't time out.

Ron W

Yes, well I guess I didn't do the job checking this system out correctly. I only checked the bags and line connections. After starting to remove the rear lines out of the vehicle, found out somebody repaired the line going to the left rear, and injured the right rear line wear it runs around the frame/chassis. They didn't repair it with a union. They rigged it with some plastic glue, a big glob. I repaired both with brass unions. Now it stays up where it belongs. I did go through the rest of the lines, all the way to the valve. Thanks to all who posted and gave their help and thoughts. This was one for the books. So now I have a new valve, new pump and new rear bags. At least I won't need to worry about those parts for a couple of years. Again, Thank you for your help.

Pmanc

Glad you figured it out now enjoy the ride

DennisG01

Good find! That's so strange that it acted just like a bag with a small hole in it. I guess the line must flex a little at the point where the break is/was? Flex one way and it opens to hole... flex the other way and it closes?

eric_in_sd

Doesn't even need to be that. Plastic is insanely hard to glue. I'd have to go back and check how you glue polyethylene tubing. Would have been so much easier just to put in a union - or even run a new line. Just fish it through.

eric_in_sd

Doesn't it make you to find out it was something little and stupid? Happened to me with a bad coil. I didn't realize that I had to reset the code to stop it from going into limp mode. Aargh.

Ron W

They glued it with the hot plastic repair iron that we us to repair the plastic washer and coolant recovery bottles

Arrie

This airmatic control algorithm is kind of stupid because the car controls its level (if too high) even when parked.

I now have two cars with it and both do the same thing, they drop after I park and close the door.

This is result of the down force that is generated when car moves. When you stop moving the car raises up as the down force goes away.

In traffic when stopped at traffic the car does not lower as the engine is running and I guess gear selector is on Drive so the car knows it will soon be moving again but as soon as I stop the engine, exit the car and close the door the car lowers to the set level. Both of my cars do this and I believe it is the stupid behavior Mercedes programmed them to do. My opinion is the Airmatic system should not do anything at all when car is turned off.

I have never seen my cars raise after i stop and exit them as I don’t think the compressor runs when car is turned off. If it did you would not see result of leaking air springs other than when it runs battery dead, which the don’t do.

I had leaks on my E-class and when this happened the car dropped over night and then raised right back up when started engine but it never ran the compressor with engine not running or ignition power on.

And it is so funny that the 1985 Lincoln Mark VII LSC that I used to have had this same exact behavior. It lowered the same way when parked and closed the door.

eric_in_sd

I don't think it lowers because there's no more down force. It lowers because your weight has gotten out. It is re-leveling the vehicle.

Now, that is a waste of compressor run time. Who cares if the vehicle is sitting funny when parked. You'll get back in and the ride height will go right back to where it was.

The reason the suspension is able to lift without running the compressor is the air reservoir. The system prefers to draw on that, running the compressor for longer intervals, with less stop-start cycles, and when the vehicle is moving, so one is not subjected to the compressor noise.