Been searching forum this week looking for a thread that describes my symptoms to no avail. If such a thread does exist please point me to it.

Purchased 2010 E550 this week. Dealer disclosed up front they diagnosed a "leaking valve" in airmatic system and ordered a new compressor. It is in writing that they completely fix the airmatic system (not just worded as "will replace compressor" )
Now this dealer is an independent that specializes in high end cars and I didn't expect them to have a complete understanding of airmatic and it's assemblies but I'm unaware of a valve on a compressor that the leak could be attributed to.I didn't object to new compressor as I figured it was good insurance to have a new one installed but the issue remains.
The symptoms:
After sitting overnight the front of the car is completely collapsed. Upon startup the suspension raises no problem. Start your driving and after 2-10 miles the malfunction indicator appears and after a few more miles the dreaded "STOP CAR TO LOW" error appears. The compressor only runs on startup. I don't hear it running while driving at all.
Leaves me two options:
Stop car, turn off ignition, open and close door, and after a minute or two the front suspension raises.
Or
Stop car, turn off ignition, turn back on, the suspension immediately begins to rise and level and while driving the "STOP" error goes away.
I've done some basic testing while dealership figures out their game plan. I've soapy water tested both front strut fittings. No bubbles. Soapy water tested the air lines the beat I could looking for cracks or pin holes. Nadda
I'm assuming the leaking "valve" is the pressure relief valve, but I'm puzzled why the compressor makes no attempt to re- level the car while driving. If I don't hear from dealer I'm going to start ordering parts.

Any suggestions, alternatives, or temporary fixes while I wait on parts and maybe the dealership?

 

There are actually several posts on here dealing with Airmatic issues. People have replaced the valve block, which is in the back under the bumper, with good and not so good results. The system is complicated enough with level sensors, pumps, valves, etc. that you may benefit from having an MB dealer diagnose the issue. I have had 2 Airmatic Mercedes and never had major issues, but understand they can be difficult to sort out.

 

it could be the "relieF valve" , but i would check the trunk and specifically the Airmatic components that are on the left side (air tank , and valve fittings) for leaking air.

yes there are multiple threads about different issues , but from the top of my head i dont remember anything with symptoms like you having,

whats the mileage? is the car sitting low in the morning after sitting overnight? i assume it works fine in Sport , comfort or fully raised?

 

69,000 miles
In the morning the front (only) is completely collapsed.
It does work in all modes. I have raised it and turned off the car to observe for leaks over a longer period of time as opposed to starting from level.

 

There was someone with similar issue , he changed the valve block (thats what even the dealer suggested i believe) but it didnt help.

Another person had a leak , and it turned out to be one the air tubes close to engine somewhere , that was cracked and leaking air , that caused it.

+ more stories but cant remember.
(me personally , the issue i had with front suspension , is that one of the struts was leaking air from a rubber boot) i could hear the air hissing sound. replaced it with a used strut.

maybe someone else will add something.

or maybe you will be able to find the right thread or figure that out yourself.

 

When they fix it, I hope they will back it for at least 1 year or 12,000 miles.

 

When the front of the car is down is it evenly down on both sides? It would be strange to have both sides low at the same time meaning that both front air springs are deflated.

To my understanding there are separate valves to each 4 air springs and when the car is not being driven these valves close. They open and close automatically when the car is used to maintain the correct level but when the car just sits the valves are closed or may let some air out if car for some reason raises up.

So, if the front is down is it really because both front air springs are deflated or is it that just one of them is?

One spring cannot hold the front of the car up if the other leaks but it should put the car in a slight angle and raise the opposing rear up slightly.

If it is just the one deflating then you may just have a leak on one of the springs and no valve issues at all or could be the valve for the one spring but this should have nothing to do with the compressor.

 

You are correct. Both in the front deflate equally at the same time as far as I can tell. Never at any angle.
If this isn't a simple fix I am going to convert to springs.

 

if you do , please give is updates. )

 

Confident there are no leaks in respective lines, line connections, and compressor valve connections consider checking for moisture in the system as a next step.

- unscrew pressure line between compressor and valve unit
- if water emerges, or if there are visible water droplets at valve unit, replace valve unit and air filter
- if no water is visible, actuate compressor with XENTRY if water runs out of the connection on the compressor, replace compressor, valve unit and air filter
- unscrew air lines from front struts and blow out with compressed air

 

So initial symptoms were 1 of the bags dropping overnight, but inflating just fine in the morning? Who being sober would conclude bad compressor?
To bring more understanding how the system work with leak:
The compressor will run for couple of minutes trying to inflate the bags and then computer shuts it down for cooling period. That will repeat about 3 times and if in that time the suspension does not come to proper level - the dash warning shows.
Per my experience the system has a flaw that will open bag valve even when there is low pressure in the line, meaning you can start driving the car with fully inflated bags, but computer will deplete the pressure on you.
Your system has clearly leak behind the compressor.

 

No, the initial symptoms were both fronts dropping. The dealer either concluded or was told a compressor replacement was the solution. I never suspected the compressor to be bad (although perhaps leaking at fitting/s) but I don't object to the insurance of a new OEM compressor.
Even before the new compressor, the front would inflate and level the car in seconds from completely collapsed to level upon startup. I do not hear the compressor running while driving.
I agree the compressor is downstream of compressor.

 

Your dealer said they would fix it. Get them to do it and keep the pressure on the dealer.

 

That is no easy task. Good luck! Be prepared to reprogram the ECU along with sourcing all of the small bits to make your conversion work.

 

It is relatively easy to troubleshoot the system once you have a way to monitor it.
If the supply lines keep the pressure, but bags drop - the leak is on the bags - plain and simple.