S212 Rear air suspension problems

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Arkangel187

New Member
Joined
May 15, 2020
Messages
25
Location
Birmingham
Car
W212 E250 CDi Blueefficiency Avantgarde
Hi all,

I'm having major issues with the rear air suspension in my 2010 E250cdi estate. To cut a long story short, I went over a tiny pothole and the passenger side rear top mount broke, also breaking the level sensor arm along the way. This resulyed in the back of the car becoming about 3ft high!! The error message on the dash said something like 'malfunction, vehicle rising', even though it was extremely high already.
I had the car towed to a garage and they replaced the top mount for the shock absorber along with two stainless steel adjustable height sensor rods, one for each side.
Everything seemed hunky dory until the next morning when I discovered that the backside of the car was virtually sitting on the floor. Upon starting, I had the 'vehicle rising' message and it rose to it's correct height. The car was then driven for several hours with no adverse effects. The next morning and every morning since though, the backside has been sitting on the floor. My local garage told me that they couldn't find any splits in the pipes and it was most probably the airbags.
I ordered the airbags from Germany from a company called Miessler and had them fitted today - however, already 3-4 hours later the car has started sagging again. I've done a fairly liquid test on the pipes and I can't see an obvious a leak....... I really am at my wit's end here.
Can anyone help shed any light on what the potential issue may be? I could always order the valve block from Germany (same company) and fit it myself, but I don't want to keep throwing money at it without getting any results.

Thanks in advance.
 
Thanks. Can you tell me why they require coding? I only replaced the rods/arms, not the whole sensor so as far as the car is aware they're the genuine plastic MB rubbish ones.
Oh, sorry I thought you had changed the sensors
 
Oh, sorry I thought you had changed the sensors

Sorry, my original post may not have been clear. I replaced both of the plastic arms of the level sensors as one was broken and the other had a hairline crack. It just made sense to replace both at the same time.
The replacement arms/rods are stainless steel and are fully adjustable, allowing you to lower your car (not something I'm interested in doing). The reason I bought the stainless steel ones is because I couldn't get hold of any genuine or aftermarket plastic ones.

I've read on here and elsewhere that the valve block could be a potential suspect as they develop an internal leak which is pretty difficult to diagnose. Would it be worth buying an £8 can of leak detector spray to see if it shows any leaks? I've already coated the valve block with soapy water and watched it for 20 mins but couldn't see any leaks on any of the 3 pipes.
 
There are two probable paths for leaks, pipe work to outside air, a split or leak at a fitting or air bag and internal leak back route via valve block check valve reservoir etc. this last path, internal leak back will be much harder to pin point. If you are confident there are no external leaks then internal leak back becomes the most probable cause and for me I'd then focus on the valve block.
 
Well I would check the pump and air tank for leaks,I only suggest this as with new airbags fitted the rear of the car is still going down not just one side when maybe a new bag is faulty,if you have checked the pump,then you have to look at the height sensor just in case it has a fault,the arm and connection to the sensor can break,it is not often that the sensor goes wrong,but maybe check ,the fuse and relay in in the boot as is the pump I think on your car
 
As a further update to this, I woke up this morning to find that the car HASN'T gone down overnight. The only things I did to it last night was spray every pipe I could see with soapy water in the hopes of finding a leak and give the valve block a few taps while checking the connections.
 
Hi there @Arkangel187

I wondered if you had a link for the stainless rods you got to replace the plastic ones please?
Thanks 👍🏻
 
Well, talking about being at your wits end! I'm there too! I have a very similar problem on my S212 in as much as I keep getting the Malfunction message and the left air bag goes down. And then the other day, the left was fine and the right went down. It's had two new air bags and ride height sensors, yet still it does it.
Any thoughts please before I bin it off?
 
Well, talking about being at your wits end! I'm there too! I have a very similar problem on my S212 in as much as I keep getting the Malfunction message and the left air bag goes down. And then the other day, the left was fine and the right went down. It's had two new air bags and ride height sensors, yet still it does it.
Any thoughts please before I bin it off?
I’d be tempted to replace the rear valve block. Quite easy to do, I did mine. If you get a non OE one just label and check the connections before you start as the new block might not have the colour coding. I got mine from Autodoc, and also bought the special tool to cut the airlines, was only a couple of quid. Changing the air lines would be my next step. I ended up changing everything on mine as nobody could pinpoint the leak. Turned out it was the airlines in the end, both sides were leaking!
 
Thanks for the reply and the advice Chris, much appreciated, I'll get on to it and report back! 👍
 

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