211 Wagon 2007 E class rear air suspension down.

[Baldbloke]

My low mileage (71,000 miles) Estate car appears to have lost pressure as the tops of the wheels are now within the arches. A message with a picture came up 50 miles from home stating 'Malfunction'. Picture of a car with arrow pointing up below car. The message wasn't in red similar to the time when the actuating rod to the axle broke and the rear suspension rose and the nose dropped. That time it told me not to drive. I probably shouldn't have driven it 50 miles home but it seemed to drive fine, although a little firmer than normal.
Now I'm OK on normal suspension jobs and most mechanical issues but have never worked on Air suspension issues. I'm certainly 50 miles from a Mercedes dealer, so would like to give a repair a go, to save some cash and learn about a car I've owned for a number of years.
The car only has Air suspension on the rear by the way.

Can anyone suggest where to start, and how to do a visual check for the problem?
Where does the compressor live?
Am I likely to KO the compressor if I continue to drive it?
Is it possible to disconnect the electrics to the compressor if I need to drive it?
Do the air lines from the compressor to the airbags give problems?
Is there a simple 'T' piece from a central line to the airbags on each side?
Could it be a solenoid or a relay?
Do the airbags actually perish and leak?
If I need new airbags do you recommend fitting a pair, or just replace the one that's leaking?
Are there any special tools required peculiar to the job of replacing the bags?
I see there are different makes, and that the Estate version seems different. Are any makes to be avoided?
Is there a spring/shocker conversion kit available, and if so, is it worth considering?

I'd be grateful for any suggestions, and input for anything I've not considered. It's never a good time for something like this to happen but I'm in for a hip op next week so not the best time for this!

 

[AndrewOl]

It can be all of the things you have suggested! The air bags on the back are a common failure point and are easy to change. Pattern parts are available which are cheaper than mb units but not of such high quality. I used aerosus on the back of my GL and they are fine. Change both if they are original. Compressor is the common point if you only have air on the rear and both have dropped. Unlikely that both have failed at the same time. The compressor usually gets noisy before it stops producing pressure. They can be rebuilt cheaply but again pattern parts are available.

 

[Baldbloke]

It can be all of the things you have suggested! The air bags on the back are a common failure point and are easy to change. Pattern parts are available which are cheaper than mb units but not of such high quality. I used aerosus on the back of my GL and they are fine. Change both if they are original. Compressor is the common point if you only have air on the rear and both have dropped. Unlikely that both have failed at the same time. The compressor usually gets noisy before it stops producing pressure. They can be rebuilt cheaply but again pattern parts are available.

Thanks for the reply.
Both sides are down, which suggests there is a leak common to both sides, or a break in the pipework. Is there a one way valve fitted to each airbag to help diagnosis?
I have certainly never even heard the compressor or know where it lives. Should you be able to hear it operating with the key on position 1 without the engine running?
All that is noticeable is the fuel pump pressurizing up.

 

[AntMB]

Get the compressor out and take a look at the piston. Also test the motor when you have it out.

 

[AMGeed]

The air pump is located behind the front n/s wheel arch cover closest to the front of the car.
If you have a pre 06 model E class the noise you hear when inserting the key is the SBC pump cycling and its normal.

 

[Baldbloke]

The air pump is located behind the front n/s wheel arch cover closest to the front of the car.
If you have a pre 06 model E class the noise you hear when inserting the key is the SBC pump cycling and its normal.

No, it's a 2007 V6 engine so no SBC. Thanks for mentioning the pumps whereabouts. I'll go there first to see if the pumps KOed and whether I've cooked it by running home with the leak.

 

[AndrewOl]

Check the ride height sensor too as I think there is only one on this model so a common point for failure. You would hear an air line leak probably and the compressor is pretty robust although will fail if running against a leak for a long time.

 

[Baldbloke]

Check the ride height sensor too as I think there is only one on this model so a common point for failure. You would hear an air line leak probably and the compressor is pretty robust although will fail if running against a leak for a long time.

I changed out the ride height sensor a year ago for an upgraded Mercedes metal one with a sealed rose joint. The original one was plastic with a corroded metal joint that sheared. The car on that occasion rose up at the rear whereas this time it appears to have gone down.

Three questions please:

I drove the car 50 miles home after getting a message on the dash that all was not well. The car is sitting low at the rear but drove home at normal speeds without wandering or giving any indication there was an issue on the handling front. If I were to disconnect the power to the compressor is there any reason why it couldn't be driven until I change out the problem parts?

1. The reason I'm asking is that I'll be in for a replacement hip this Monday and the wife's car is also playing up and I don't want to have to complicate matters by having to buy another car in the meantime, if the Mercedes is useable.

2. Is this conversion worth a go and has anyone here done it?
Mercedes E-Class Wagon 03-09 - Arnott Rear Coil Spring Conversion Kit W/O ADS | eBay

3. On other sites similar Arnott conversions say their not suitable for the Elegance model (which mine is) and yet this one has no exclusions as long as it the model with air suspension only on the rear (which is like mine).

 

[Baldbloke]

Further to my wish to explore the Arnott spring conversion setup to get away from the air suspension I rang Arnott directly. For some reason the Elegance is the one model that they do not cater for. They state that their spring does not conform to the correct ride height. So that's out of the game then.

Presently looking at these: Mercedes-Benz W211 E-Class Estate Rear Air Suspension Spring Bag (w/o ADS) | eBay

 

[AntMB]

Isn't Elegance just a trim level? Why would it be any different to the Avantgarde?

 

[AndrewOl]

If it just the air bag(s) they are £100 each from aerosus I think and they will last another 10 years with any luck. Bad timing for car trouble for you. Hope all goes well with the op. If the bags are flat on the back I wouldn’t drive it.

 

[Baldbloke]

Isn't Elegance just a trim level? Why would it be any different to the Avantgarde?

That is what I thought but Arnot actually mention in their sales brochure (and over the phone when I asked for clarification) that the spring kit that fits all the other models but mine.

I personally would have rather de-complicated it for reliability.

 

[Baldbloke]

If it just the air bag(s) they are £100 each from aerosus I think and they will last another 10 years with any luck. Bad timing for car trouble for you. Hope all goes well with the op. If the bags are flat on the back I wouldn’t drive it.

Just looked them up thinking there was a two hundred quid saving but it seems they're £260 each for the T model Estate:

Mercedes-Benz E Class S211 / T-Model (without ADS) Rear Left Air Spring - A2113200925 | Aerosus

 

[Baldbloke]

I still haven't got around to diagnosing it yet but wonder if this could be something unrelated to the airbags, as it is equally down at the back. Both appear deflated and I would guess that a simultaneous failure of both is unlikely? I would have thought the airbags would have had one way valves and if an air bag had failed it would sit up on the remaining good one? It is air suspension only on the rear by the way.

 

[AntMB]

I think the valve is only at the compressor. The best thing to do is look for leaks from the pipework on the way to the compressor and check the compressor.

 

[AntMB]

I think the valve is only at the compressor. The best thing to do is look for leaks from the pipework on the way to the compressor and check the compressor.

 

[Baldbloke]

I think the valve is only at the compressor. The best thing to do is look for leaks from the pipework on the way to the compressor and check the compressor.

Thanks for that. That could explain why both sides are equally down then

 

[AntMB]

On your way long the pipework somewhere up the front I think around the passenger floor area underneath, there will be a manifold block, (if the '07 is like the 2003 ones).

 

[millo777]

I'd start by checking the relay for the compressor. They are only about £15 from the dealer, and are a common fail point. If needed you can always jump sockets 30 and 87 on the relay base to see if the compressor kicks in.

The splitter manifold that sends air to both springs is mounted on the rear subframe just in front of the diff. Easy to get to if th rear of th car is jacked up.

Compressors are straight forward to rebuild, but I'd recommend changing the filter as a matter of course. They tend to let grit into the system that scores the cylinder head and piston ring and reduces compression.

 

[Baldbloke]

OK guys, thank you all for your inputs.

I'm just out of hospital with a new hip, hence the delay in getting back to you, and why my fault diagnosis has been delayed.

The car in the intervening period has sunk even lower down at the back. Lower than it was before I went into hospital, so there's definitely a loss of pressure. On firing up the car it slowly rises but not to what it should do. The car only has air self levelling suspension on the rear of the car.

I would like to get away from the air suspension and instal a spring conversion kit from Arnott but have been told (By Arnott) that the Elegance model (mine) is unsuitable for this conversion although their site suggests its good to go as long as it is for the estate car which doesn't have ADS which I'm presuming is air suspension all around on both axles. Mine fits the correct description to be able to take the kit. Why would my Elegance model be unsuitable when an Avantguard would take the conversion? I would have thought that the suspension maybe a little softer on my Elegance but cannot see the main components (wishbones/mounting points etc) being different between the trim levels.

I'll put in an additional thread to ask about the differing types of suspension available

Am I wrong?