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Air suspension issue w211

ChrisMartin

New Member
Joined
Sep 22, 2019
Messages
4
Location
Croydon
Car
280 cdi sport estate
Hi I'm a new member and am seeking some help with the dreaded air suspension. My 2004 cdi 270 elegance estate started dropping on the rear, drivers side whilst parked. It wouldn't do it all the time but once every 3 to 5 days. As soon as You started the engine the compressor would cut in and raise the car it wasn't low enough for a warning light on the dash but it was obviously noticeable. I took it to my Mercedes mechanic who put it on a machine to test and he said the air bag had a leak and would need replacing. Merc do a reconditioned option for £340 so I told him to order it. But before I could take the car back the other side started dropping and it was low enough to give the red warning notice car too low. Again once started the compressor would raise the car and it is fine to drive. I called my mechanic and told him the other side was now also going down he said it would be better to replace both bags. Now that would cost around £1000 including labour so I've decided not to have the work done and have gone and purchased a 2007 280 cdi sport estate. The funny thing is that in the last two weeks the 270 cdi has not dropped at all. Which has me scratching my head, surely if the airbag or bags had a leak it would always be dropping not occasionally ?? . Or is it just a sensor fault ??. I've used this merc mechanic over the last two years and never really had any cause to doubt him but this issue has me wondering. Can anyone out their confirm that a air bag leak can cause a intermittent fault.
 
Well the only way the car knows what the height should be is by a sensor,so it could be a faulty one,on the S mercedes it is over the rear axle and has a rod which attaches to a sensor and that sets the height at the back,you car may have two sensors I have no idea.
 
Well the only way the car knows what the height should be is by a sensor,so it could be a faulty one,on the S mercedes it is over the rear axle and has a rod which attaches to a sensor and that sets the height at the back,you car may have two sensors I have no idea.
Me neither, I wasn't aware that the car may have two sensors.
 
The Mb units have check valves which are shut whilst parked , if it go’s down whilst parked I’d say the units are faulty, it could be alloy corrosion where there rubber pipe mounts strut to air tank, the alloy pipe connector can be rubbed down filled with a epoxy chemical metal and should seal up the leak. Tbh I’d be inclined to fit 2x new arnott units which do away with the tank. Also the compressor may be well worn if this has been going on a while.

All s211 ‘s have air suspension on the rear so don’t be surprised if your replacement vehicle needs a new pair at some point.
 
I just found it strange that if it has got a leak then why is the suspension only dropping now and again and not every time the car is parked up for a couple of three days. It's only been happening recently so it hasn't as yet affected the compressor. I'm selling the car now and will of course tell any buyer the issue I've had with the suspension. I checked on the arnott site for the cost of their replacements but couldn't find a price. Are they significantly cheaper. It would be good to know as you say even my new car may well need the bags replacing in the future.
 
Is it full airmatic suspension you have or just self levelling rear suspension with just air springs at the back?

I have a 2006 s211 with air springs only at the rear and it behaved exactly like yours. Would stay up for weeks and then one day I would find the rear offside had dropped. In my case this was usually after a prolonged period of not being used. This behaviour seems common if you start searching. After the third or fourth drop I bit the bullet and replaced with a pair of Arnotts which have solved the issue. I bought these from a German eBay seller and they were £463 delivered. If you switch to Arnotts it highly recommended to change as a pair.

Good luck and hope this helps.

BTW I am a bit suspicious of the solenoid valve on the "faulty" unit as when I ran a compressor test from Star disgnostics the rear rose slightly potentially indicating the soenoid valve might be leaking.



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I believe it's full air suspension as my 280 sport is self leveling and I can definitely notice the difference in the suspension. My 270 cdi has exactly the same problem as yours had so its reassuring to know my mechanic did diagnose it correctly as the airbag needed replacing. He didn't however give me the option to replace with the arnott ones which would have given me a big saving on the merc reconditioned ones. Hope I don't have this issue any time soon on my 280 sport.
 
On your sport you can change out the rear self levelling air bag units for a coil spring conversion. On an Elegance estate/ wagon you cannot.


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Mine did exactly this (went down occasionally on one side, and even more occasionally both sides, but pumped up again). Was traced to a very small leak in one of the pipes, quite difficult to find. However, a relatively cheap fix in this case and no more issues. So not necessarily the air bag itself, and cheaper to check the pipes (carefully) first I think!
 
Mine did exactly this (went down occasionally on one side, and even more occasionally both sides, but pumped up again). Was traced to a very small leak in one of the pipes, quite difficult to find. However, a relatively cheap fix in this case and no more issues. So not necessarily the air bag itself, and cheaper to check the pipes (carefully) first I think!

Yes, absolutely agree! I was advised by others to check over the rear subframe for cracks. But mine had a leak about a foot away from the compressor, under a retaining strap.


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Hi Chris
Mine did this. Intermittent dropping of one side at the rear. My understanding is that it turned out to be a "sticky" valve so the dropping was unreliable. I had to have a new unit.
I'm about to put another post on here about this.
Hope it helps.
 
Hi Chris
Mine did this. Intermittent dropping of one side at the rear. My understanding is that it turned out to be a "sticky" valve so the dropping was unreliable. I had to have a new unit.
I'm about to put another post on here about this.
Hope it helps.

Look forward to reading it! I've had airlines replaced, but still same
 
I'll see what information I can get about this when I pick the car up later.
In a nutshell, it did it again a year later and then within weeks the 3rd unit burst inside the casing.
 
I have an E320 estate (W211), with steel front springs and rear air filled self leveling struts, it is sagging on the rear left hand side, but does not pump up when the car is running, the local independent says that they have "pumped it up manually" and that I should first "suck it and see", well its dropping again, 1 1/4" overnight measured at the wheel centers to wheel arch lip. Its been like it for a while, maybe a year or longer, but a week or so ago when I viewed the car on very level ground it seemed worse, maybe 2 1/2" inches lower, there are no dashboard alerts showing, where is the ride height sensor and is there one for each side?, any other offers of help? Would I be able to hear or fell the compressor running, and where is it located
CLEM
 
I think there is only one on the Rear of the car from memory, Bolts on the inner Rear arm Subframe area on the Left hand side there is a adjustment rod just above and forward of the rear differential.
 
I think there is only one on the Rear of the car from memory, Bolts on the inner Rear arm Subframe area on the Left hand side there is a adjustment rod just above and forward of the rear differential.
Thanks, I will take a look, if you are correct and there is only one ride height sensor, and its in the center of the car near the diff, it might not be what I am looking for, the right side stays up, ok, its the left that drops, but also it doesnt pump up? but reading through previous threads it seems I may have a leaking (very slowly) check valve, its the left hand rear that is dropping, but it stays dropped, where is this check valve? any ideas why it doesn't pump up?
CLEM
 
where can I find the check valves for the air bags, could someone post a photo, since the left rear of my estate drops only a little and stays there, leaving the car usable, just a bit lopsided, I don't think this is an air leak, because if it was, even a tiny leak, and the bag would continue to lose air and drop onto the stops, it only sags a little, so maybe a slightly duff check valve that can hold "some" pressure, but not enough to maintain the full height, seems more likely to me anyway.
CLEM
 
surprised that no one has answered this one for me yet,
#looking to remove and replace the check valves for both rear air bags, but where do I find them, and the compressor and the control valve body.
many thanks
CLEM
 
I can only talk about the S211 or estate version which has self-levelling rear air suspension. The most common cause is a leaking airbag and yes, strangely enough, it can indeed be intermittent. Just be aware that the air compressor does not like being over-worked and if this issue is not rectified, then be prepared to be charged for that on top of the cost for the defective part.

I have heard of so-called 'specialist' garages charging customers for all sorts of items when they try to fix this issue by 'trial and error'

I had NO idea how an air leak could be intermittent but we live and learn. Our car was parked with a main dealer for ten days before the thing finally decided to sink. thankfully Mobilo had been called out, witnessed the car down on the nearside rear-end and they had the car removed back to their workshop and we enjoyed driving a number of courtesy cars :)
 
surprised that no one has answered this one for me yet,
#looking to remove and replace the check valves for both rear air bags, but where do I find them, and the compressor and the control valve body.
many thanks
CLEM
Take it a decent indy that knows what they are doing :thumb: Or try the search function on the top RHS of the page and immerse yourself in the numerous threads on air suspension faults on the 211, 219 etc etc.
 

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