Denis Osullivan

Does your car remain at the same height overnight.
I’ve arbitrarily measured and find that the car lowers itself by as much as 1/2 inch over night.
Is this normal or just the beginning of a more serious issue?

Wolfman

This would be considered normal

MBNUT1

The puzzle for me is that doesn't the airmatic drop down when you turn it off for ease of entry / exit and does it drop down further after you get out? I am assuming that the poster is measuring it with it off and out of the car so I don't understand the additional drop.

Wolfman

Our airmatic always adjusted when parked. The initial leveling after driving up our steeper driveway and some settling over time. Not big questionable drops like the in the old days (W220) but a little bit. Had it overnight or weekends.

kafklatsch

The system has a pump that actuates periodically when the car is driven, and it also operates continually at startup IF the car is not at correct right hide.
logically this means that the "psuedo-closed" system has to leak in some way - by design, because if it where a truly closed system you would not need a continually available AND functioning air supply

all of my S's have dropped a small amount when parked. I remember checking one of my cars years ago, and the drop happened pretty soon ( an hour +/-) after I turned the car off and it stayed there pretty indefinitely.

The small drop will typically be noticeable to the attentive eye but otherwise appears normal.

My old ABC (hydraulic) S55 w220 would sit on the front tires (or was it the rear?) and IT did require repair..... I do recall that in all the time I had that car, this and the mass air sensor were the only issues the car ever had.. rock solid..

FUN WITH MB: sit in your car with your car running and turn so that your feet are on the ground.... over the course of a few minutes you will feel the car rise and fall... even more noticeable after the new is worn off (havent tried it for all my airmatic cars but it also did this on the hydraulic cars)

2012 merc amg

As I remember if you turn the car off and park it in the raised height position from the button with the car on it on the left side of the center console the car will stay in the raised position until you hit the button again when the car is in the key on position.

SW20S

Very normal. Mine pumps up some every time I start it up.

Felt this this afternoon after I washed it!

SilverArrow44

Much like the air pressure in your tires, the air pressure in the Airmatic strut changes by a few PSI based on ambient air temperature. Your pump will activate when you start the car to pressurize the system and bring the vehicle up to normal ride height.

However if you come out to your car and the top of any tire is completely buried in the fender, then there's a leak in the system - mostly likely the strut. And if that starts to become the norm, then you're close to failure. The system will do its best to compensate for a component that's leaking air, but that starts to put stress on the pump and the pump relay.

So if the change in height is minor and immediately adjusts to normal upon startup, then you're okay. But if the change is significant and happens quickly when the car is off or happens often when the car is off, then you need to get the Airmatic system checked.

kafklatsch

As an inquisitive engineer, I too thought it was the ambient temperature, but I did the following years ago, I ran the car when it was about 60 degrees outside late one night, I then checked the car height several days later when it was 96 F outside and the car was still lower by a bit. It was an experiment for me. Another time I drove the car around with a scan tool connected, and it would show the pump come on periodically to correct ride height with no apparent change to the ambient temperature. That fact this this periodic activation repeats for a car with no "drop" issues gives some insight into the system.. just my humble insight .

Denis Osullivan

The dealer just replaced my Airmatic strut as I complained that it was loosing some air (not a lot) overnight as well as hearing a slight clunk if the car was raised and just slowly going over a few bumps. Repair was covered under warranty. Sometimes it pays to have a little OCD. lol

Nice Ride

In my 2014, If I park it in the raised height with the button, about 15 to 20 min after turning the car off, it will drop to the lower position. After starting back up, it will raise back. Note: for the 15 to 20 minutes after the car is off, the car will not drop at all, its only after the times passes that it will do the drop.

audioneurotica

As it turns out one of the height adjustment sensors was broken off. It sounds like that and the new struts will hopefully do the trick, but I'm still keeping my fingers crossed. thanks for all the feed back, Will

w126w221

Normal, Normal, Normal. System is based on the W221! They are designed to re-level the vehicle after occupants have left, thus reducing stress on the system. Some people report it even purges the entire residual charge tank, however I am not certain. I will do research on this tonight and I can post the Mercedes documentation of system functionality. One thing that begins to annoy people, with vehicle age, is the purge valve will make a very rapid whoosh. I don't know how to resolve this other than replacing the air compressor, as replacing the inlet hose and filter did not fix my issue. It has grown on me a bit and I laugh some days, because sometimes it sounds like a squeaky fart, while other days, it highly annoys me.

w126w221

I did this exact test, but with my 2004 Audi A8. The diagnostic system would allow you to add compressed air to each four corner air springs, and at the very last instance flash the Pa value, following up there was a function to read the current Pa value.

So after driving the car extensively, I'd lock out the suspension (MBs can't do this?), add a set amount of air, and then allow the car to fully go cold approximately 10-14hrs. After checking the pressure the next day, I found a unique anomaly, as the pressure drop wasn't decreasing by the rate of ambient temperature drop, but something more significant. What I failed to factor in is that, air temperature within the tire well and physical temperature of the axle assembly is higher than ambient air surrounding the vehicle. So, I took measurements of the air temperature of the wheel well, and axle assembly, and used the higher value. After this the pressure drop with respect to the parts and surrounding area acclimating to ambient temperature of the city, the pressure drop was normal with the calculator I was using.

P.s. I am also a very inquisitive engineer.

cfmistry

Mine "re-levels" after after I have closed the driver's door. It usually airs out about 0.5". That may be due to the slant of my garage. Or not.