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[W212] Airmatic Rear low after parking

cezar

Active Member
Joined
Aug 1, 2019
Messages
114
Location
not UK
Car
W212 E350 CGI
Hi

no problems with airmatic until now (at least 15k km in about 4 months with no misbehavior). Two days ago I found my rear end dropped all the way down equally on both sides. Once started the engine is back up in 10-15 seconds and stays there without the pump working (from what i can tell).

When parked it drops again. One time in no more than 15-20 minutes it was low already. One other time it was still up after one hour but dropped in the next half (i think it was on high position from the cabin).

This morning again low. I start the engine and it brings it up. Driving gives zero errors. Pushing the raise button works. Although I have a feeling now it only works on low speeds (not sure it was the same all the time or just now). Parked it after one hour drive and checked again after one hour. The rear is low (but doesn't look always the same low position). What's strange though is that the front seems to high (like when you manually raise it).

I will make a dealer visit but i was hoping for some advice here. The dealers tend to keep the car indefinitely and who knows what and if they fix it :(

thanks
Cezar
 
update:

after being parked for 7-8 hours it was low but not as usual. not that obvious as two days ago. Opened the car and started the engine it raises with no problem. drove for approx one hour, highway. al good. at home tried to watch a bit. all seems fine. goes up and down as it should. no noises. no pump running for no reason. no audible air leaks. parked it front first now as there is a slight slope. let's see tomorrow morning. left on low position and took some pictures.
 
I'm going through the same thing. Trying to diagnose a similar issue but no conclusions yet.
 
update:

this morning again it was low on rear (see pictures). Front was fine and dandy.

Friday I have an appointment for regular maintenance (B package) and I’ll open this topic, although I don’t expect much coming from this unless I leave the car there.

Posting from mobile and it seems the pictures are rotated 90 degrees. Sorry for that

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update:

9 hours parked and now looks much better. Very low drop. You can see here a before and after engine start. It looks like parked there behaves different compared to parked home. Home it looks like the front is way higher. gonna post again tomorrow.

anyone experiencing something similar?

IMG_8630.jpeg
IMG_8631.jpeg
 
i was posting in another thread... two days before i first noticed this behaviour i replaced one xenon buld on the driver side. to do that i disconected a "thing" in order to get access (see the pic under the bonnet behind driver headlight). and i pushed it on the side. i think when checking the lights i also started the engine ones with that thing still disconnected. of course at the end all was put together. but is that part of the airmatic system? could that have an influence?

IMG_8539.jpeg
 
If you had an electrical fault its likely you would get a warning message on the dash. Most likely explanation is a slow leak somewhere but at present not enough to flag a fault.
 
got it. thought so but wanted to double check.

it seems i'll have to rely on the feedback i get in service end of this week when i go for regular maintenance. i'll ask but i'm not to confident.

anyway it's strange how the behaviour is not constant. like one time all the way rear down. sometimes just a bit. sometime front way up. other time normal, or just a bit... and all combinations.
 
update:

parked again during the day roughly 9 hours and the car looks ok. a bit lower but not much at all.

drove approx 1 hour and 80 km (highway and traffic) and parked in an underground mall parking. after one and a half hours getting back to the car it looked just perfect (i left it in the up position because of the parking access and bumpers).

went back home and parked. waited a bit close to the car. have to mention that home parking spot seems to be inclined a bit (the nose a bit lower than the rear). in less than a min i could hear air being released form the rear. two times i guess with longer hisses. and one or two times with short more powerful strokes (like and overpressure valve being triggered). in all this time i could here a click clack noise which i've always thought to be the car body "de-stressing"... but it was quite regular, like click click click every second or so. seemed to come from the rear somehwere in-between the wheels.

and that's it for now. Friday i have an appointment in service and i'll ask about this. will report back.
 
short update again:

car now behaves, I think, normal. it just sits proper with a slight drop (1cm'ish?) over night/day. tbh that drop might have been as well before all this as i started to pay attention only when found very low.
 

i've been reading through this and it's really nice one. what's a bit confusing is that it seems to be two systems: SAS and Airmatic, right? and going through it says that during parking normal variation is 0 mm +-10, and even so the car will correct this when starting only if it is more than 30 mm lower than normal. What I haven't seen is how the self leveling after parking works. I understood the car does that once parked. That would be interesting to see how it is processed and what take into consideration.

in other words coming back to my first post i realized today that in those two "critical" days in which it dropped more those were two days with much lower temp outside compared to now and before: before it was 5-8 degrees over night, that days was zero and a bit below, now its back to 4-6 degrees over night. could that be a hint of some sealing problems? maybe it's stupid but I imagine if there is a very old "rubber" it might behave bad in a close to freezing temperature environment.
 
status update:

been to dealer for regular servicing. also asked about the airmatic issue and of course they have to keep the car overnight to diagnose, which was not possible now. but they did a xentry check (or what the name is) and at least there's no error there. will have to go to finish the other tasks from my regular maintenance and I'll ask for a full check

in the mean time it looks ok. no more full drops or anything. seems like maybe it drops 5-10 mm'ish over night but other than that is ok.

we'll get back when more details are showing.
 
18 hours in and it looks visually ok. 5-8 degrees out although the service guy told me it should be different on low temps.

i measured the heights (to bad i didn't do it last night :( ) and it shows like in the picture (RL, RR, FL, FR). will measure again in 24 hours and update here.

IMG_8744.jpeg
 
24 hours in and the measurements show like this

RL 0,65 (-3cm), RR 0,65 (-2cm), FL 0,65 (-1cm), FR 0,66 (-0 cm) - keep in mind my laser ruler can't go down to mm in terms of precision

temps over night close to zero

clearly there is a leak :( strange it all varies and i'd be surprised to just have all sides broken simultaneously. i hope at least is a central thing that can be easily repaired/replaced, although from what i understand each side is separately locked/closed.

anyone knows if one side has a leak will it force the others to drop as well?
 
Last edited:
parked it this evening. 3 hours later and the back is another 30mm lower. and all happens today when temps dropped bellow zero again. Definitely gonna need some replacements in the rear are :( the front stays pretty firm on position.

tomorrow will talk to service to ask for repair. will be tough with the holidays coming :(
 
this morning all the way down in the rear. clearly temps have a saying in that (-4C degrees last night).

doing a bit of research I came upon an interesting bulletin that confirms the temperature influence to a certain degree (it can lower but not to much - that's actually physics)

extract (full document attached)
1. Check:
Park the vehicle outdoors and after approx. 2 hours, when the vehicle has cooled down, measure the vehicle level at the rear axle on both sides from the wheel center to the fender.
Note: The vehicle level can drop by 1 mm for each 1°C of temperature change. For this reason, wait 2 hours before measuring the vehicle level in order to rule out the influence of temperature.
2. Drop in vehicle level overnight less than 15 mm:
The air suspension elements are OK. It is not necessary to replace the air suspension elements on the rear axle.[...]
3. Drop in vehicle level overnight greater than 15 mm:
Check pressure line connections at valve unit and rear axle air spring for leaks using a leak detector spray. If leakage is found (bubbles forming), replace the defective component. [...]

P.S. sent message to dealer and waiting for answer.
 

Attachments

Well it is normal with the rear airmatic way down after it has been left a while to get a message on the screen saying theres a fault and see the MB garage,now you are not getting that,and you say it is more at the rear and the front is not going down hardly at all,I am sure you have a level sensor that will be located above the rear axial,now this does not put up a fault like the pump if it is faulty ,the sensor is just a small box with a arm that attaches to a bar,if you put lots of weight in the boot it is this that tells the pump to put air into the system and also to take air out,it might be worth checking that this is tight and the electrical connection is secure also check the arm,these have a habit of cracking,anyway well worth a look before MB start changing air bags along with a big bill.
 
i'm also concerned about MB bill coming up. I'd say it's a sensor as well, although a full diagnose done in service last week showed no errors.

what is strange is that is directly linked (or at least it seems so) with the negative temp outside. it happened two times (one week apart) to get all the way down and both times there were negative temperatures outside.

this morning it was all the way down as i said and it just leveled fast and nice when engine started (NO red error code in the dashboard - maybe if it sits longer to get even lower). parked at work now, 7 hours in and it look like all is fine and dandy... this is the reason I'd say it's a leak. A sensor would've behaved different I think

anyway, I need to fix it as this is my everyday car and more than this holidays are coming and also much lower temperatures. got in touch with service today and I'm waiting for feedback when i can get it there. they'll keep it over night and measure themselves and than they wanna make some pressure checks and conclude. let's hope for the best. at least last week they didn't changed the front disks as I thought it's needed and they recommended the change for next set of pads. so I can only hope they're not there to rip me off.
 
When I had a sensor failure the rear dropped all the way down without any warnings or messages and the pump didn't engage at all. S212 completely sagged but no messages
So I doubt this is the cause in your case since the pump fills the bags after start. More likely there is a slow air leak or a fault in a valve block for rear lines. But again as you found out it can be nothing but only the influence of low outside temperatures.
 

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