E350 rear air suspension trouble - not Airmatic

Roger57

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Hello everyone,
I have a 2011 E350 estate which has recently developed an issue with the rear suspension. No message appears on the dashboard, but if the car is left overnight the rear suspension drops slightly. After two days it has dropped a little more. When the engine is started the car slowly rises and again, no fault message is apparent. I have had the car about two years and do not recall seeing this until recently.

I know that this setup uses a small compressor to raise or lower the car according to the payload. The compressor definitely works (I can hear it) so obviously I have a small air leak from somewhere.

Does anyone have previous experience of this issue? Given that it is only a small leak and both sides of the car drop, I suspect that it may be a hose or valve problem. Where is the compressor situated?

I know that replacement air springs are not cheap but I would like to check out the rest of the system before I take the car to my MB specialist.

Both of the plastic sensor links have been replaced last year. Once the car has been running for a couple of minutes the suspension is at the correct height on both sides according to my iCarsoft scanner.

Could anyone assist please?

Thanks
Rog
 

EmilysDad

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I can only suggest a squirty bottle full of soapy water liberally sprayed around any & every airline & connection you can find ... obviously as you imply, it could be the air bags/springs that have failed.

Merc wanted something like £400+ each side to just supply an airbag for the rear of my R Class, I had Arnott pattern bags fitted at an indie for around £370 each side.
 

Jkh112

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Sounds similar to the rear suspension problem I had on my E class estate. Mercedes fitted two new rear airbags (under warranty) and all has been good since.
 

steveq

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The air suspension units at the rear are probably the originals and so coming up to 10 years old.
They are rubber cylinders that hold air at high pressure.
They perish over time and the rubber splits. This is exacerbated when they lose pressure and the rubber flexes excessively.

It is worth using soapy water on the air lines to the valve block under the rear bumper and from there on to the air bags. If there are leaks in the air lines it will be an inexpensive fix.
If it is the air bags themselves it will be more expensive to repair. It is DIYable if you are up for it and there are third party suppliers who sell replacement units which are significantly cheaper than MB prices.
I replaced them on my 2011 S212 with similar symptoms about 4 years ago so you're not doing badly.
 
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Roger57

Roger57

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The air suspension units at the rear are probably the originals and so coming up to 10 years old.
They are rubber cylinders that hold air at high pressure.
They perish over time and the rubber splits. This is exacerbated when they lose pressure and the rubber flexes excessively.

It is worth using soapy water on the air lines to the valve block under the rear bumper and from there on to the air bags. If there are leaks in the air lines it will be an inexpensive fix.
If it is the air bags themselves it will be more expensive to repair. It is DIYable if you are up for it and there are third party suppliers who sell replacement units which are significantly cheaper than MB prices.
I replaced them on my 2011 S212 with similar symptoms about 4 years ago so you're not doing badly.
Steve,
Thanks for the reply. That is a bit of a worry; I assume that an affected air bag could completely fail at any time.....
Your vehicle is an S class; obviously a saloon car and I suspect that the valve block that you describe will be located in a different place on my E350.

Does anyone know where the valve block and compressor are located on this vehicle?
 
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Roger57

Roger57

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Steve,
Thanks for the reply. That is a bit of a worry; I assume that an affected air bag could completely fail at any time.....
Your vehicle is an S class; obviously a saloon car and I suspect that the valve block that you describe will be located in a different place on my E350.

Does anyone know where the valve block and compressor are located on this vehicle?
Sorry, I have just read another post by yourself and now realise that your S212 is actually an estate car....
 

malcolm E53 AMG

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Judging by the amount of rear airbag failures on 11 plate S212s I suspect that the early cars had quality problems in the manufacture of these units. I’ve seen a lot parked up on my travels sat on their haunches if left for a couple of days and nearly all posts on here have related to 2011 failures. As said in another post today the rubber bellows tend to crack in the creases resulting in some cars loosing pressure every time the car is parked up or sometimes depending on whether the car is sat on uneven ground.

Better to get the bags replaced sooner than later or the air pump will burn out through overuse. The air pump is situated at the back of the car behind the rear axle beneath a plastic cover and the relay is situated behind the cargo area drop down panel passenger side where you will find a cutout in the trim
 
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Roger57

Roger57

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Judging by the amount of rear airbag failures on 11 plate S212s I suspect that the early cars had quality problems in the manufacture of these units. I’ve seen a lot parked up on my travels sat on their haunches if left for a couple of days and nearly all posts on here have related to 2011 failures. As said in another post today the rubber bellows tend to crack in the creases resulting in some cars loosing pressure every time the car is parked up or sometimes depending on whether the car is sat on uneven ground.

Better to get the bags replaced sooner than later or the air pump will burn out through overuse. The air pump is situated at the back of the car behind the rear axle beneath a plastic cover and the relay is situated behind the cargo area drop down panel passenger side where you will find a cutout in the trim
Malcolm,

Thanks for the info.
So the pump is actually in the N/s wheel well on the E estate....I can hear the pump when it is running but without groping about in the snow I couldnt actually work out where it was.

The one thing that I dont understand is why there is no error message on the dash saying that the suspension level is out of spec...nor are there any recorded error codes.

Whilst I appreciate your (and some others) evidence that one or both of the airbags will be the culprit, and obviously I will replace both if one is leaking, surely it is worth checking the pipes etc for leaks first....?

Does this car have a valve block/manifold and if so, do you know where it is...?

Thanks
Rog
 

malcolm E53 AMG

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The pump is behind the rear bumper sited slightly over to the nearside you will need to remove the underneath splash panel to access as far as I know the valve block sits adjacent to the pump. There is a level sensor sat next to the rear axle. Yes always worth looking at the inter-connecting air pipes but not many reports of pipes splitting or leaking etc

Good luck with it it’s a PITA with such a ‘young’ car

ps better to replace the relay at the same time circa £10 so cheap to do and keep the old as a spare in the car. The error message generally appears in the dash when the bags have more or less fully deflated
 
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Roger57

Roger57

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Yes,
Even more a pain when there is snow on the ground and I cant get it in my garage....

This car has two level sensors, one for the right and one for the left. Earlier this year I was driving home from work when there was a bump and the level error message appeared. Only a mile from home after a 150 mile drive....lucky..

Rear suspension had dropped the car to the bump stops. Turns out that one of plastic sensor links had broken. I made two new ones from 6mm S/S threaded rod and the ends from a couple of old gas struts.

For a while (a few thousand miles) all was OK. Took the car to a wheel specialist to have the wheels done (one was buckled) and the car seems to have had this problem ever since....
 

steveq

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Hi Roger,
Merc designate their estate cars as "S" so our model of the E class estate is S212 whereas the saloon is the W212.
Possibly the collapse due to the break of the height sensor triggered the failure of the air bags?

I saw that one supplier will sell a pair of airbags for about £350.
 

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