W211 270 Estate... Suspension Air Chamber

[Nthkentman]

Ok.. I have ripped the entire rear end apart inside, and cannot find the pressure chamber... Does *anyone* have an inkling where I might find it to inspect it please?
Replaced a shot NSR air suspension unit, and cleaned the pump and fitted new piston seal ring in the pump on the piston, air gets to the Y branch at the back, no leaks in either side fittings at the suspension units... Still won't pump up... Staying on bump stops... Could it be anything else ?

 

[Borris1954]

Is this airmatic or just self levelling rear suspension? In the later case there is no reservoir.

If the pump is working and air is getting to the rear but its staying down and you cant hear any great hiss of air that suggests to me the solenoids on the air bags may be remaing closed.

Can you hear them click?

Good luck.

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[Nthkentman]

Is this airmatic or just self levelling rear suspension? In the later case there is no reservoir.

If the pump is working and air is getting to the rear but its staying down and you cant hear any great hiss of air that suggests to me the solenoids on the air bags may be remaing closed.

Can you hear them click?

Good luck.

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It's the rear only system, not full Airmatic.... When I open the boot or doors, the compressor start up just the same as if I start the engine. The system just stays low on the stops. Can'rt hear any leaks, and I know the air is getting to the joint under the rear seat, and also to the Y branch. I'm really puzzled as to why it's not even trying to lift. Is there anything else in line which may affect the system ?? Would a faulty height switch be a problem ?

 

[SteveK9]

Does the compressor keep on running or does it stop after a few seconds? Have you measured the air pressure in the pipe? Yes faulty sensors could cause the issue, have you tried supporting the car at normal ride height after a battery disconnect for about 15 minutes then turning ignition on and starting engine?

 

[Nthkentman]

Does the compressor keep on running or does it stop after a few seconds? Have you measured the air pressure in the pipe? Yes faulty sensors could cause the issue, have you tried supporting the car at normal ride height after a battery disconnect for about 15 minutes then turning ignition on and starting engine?

Compressor sounds as if it's running fine.. Not measured pressure tho... But it's a healthy blow from the open ended plastic 4mm tube at the Y branch. Not tried the idea of supporting the car at the correct ride height yet...I'll try that idea, but unsure why that might change anything...But I'll give it a go... I'm leaning toward the level sensor mostly. All this started when the NSR gave out (After a few weeks of slowly lowering, but pumped back up most times) so replaced the unit, then the new one went with a loud pop, which dumped the suspension onto the stops.. I wonder if the level switch suffered in the process...I hear clicking from the rear end sometimes as it *tries* to inflate, but fails

 

[SteveK9]

If you're getting a good supply or air it's probably fine but I have had a pump that wouldn't give much pressure only volume and gave similar symptoms to yours. You say your air spring went with a pop, don't know if you saw what happened to mine Stop car to low..... (a 212 not a 211 but I had a pair of those previously). I wouldn't have expected it to screw up the level sensor but I am assuming that you have the too low warning on the dash and if you support the car at normal height and it goes off you can rule out the sensor, if it is not on in the first place then there is a good chance it is screwed but supporting at ride height after a soft reset can sometimes wake it up if the electronics have lost the plot after a sudden failure. Why this happens is beyond me but I spent an age and ended up disconnecting the control unit for a while (front nearside footwell) and it cured it but apparently a full battery disconnect will do the same but then you do have to re-set up various other things. Clicking from the rear implies a valve operating but you definitely have no air to the tube going in to the spring, it's not just that it's failing to inflate?

 

[Alps]

on full airmatic its behind the rear qtr right hand side, as its semi, it might only have the chambers next to the spring units, these corrode where the pipe joins, but can be repaired with a bit of ali weld or temp weld putty.

 

[Nthkentman]

on full airmatic its behind the rear qtr right hand side, as its semi, it might only have the chambers next to the spring units, these corrode where the pipe joins, but can be repaired with a bit of ali weld or temp weld putty.

Seems like there are no pressure chambers on mine at all.. The suspension units are the 2 pin versions, and I can't find the air tanks anywhere, even underneath

 

[Borris1954]

Thats correct yours (like mine) is quite a simple system.

MB are very clear, as are Bilstein and Arnott if you watch their installation videos on YouTube, that the air springs are inflated before the wheels are put on the ground and suspension fully loaded. This may be why your first new spring went bang.

I replaced both mine using Star and following WIS instructions. Inflating the springs is basically a six step process. 3 steps for each side with each side being done separately. Without Star I think you could do one side at a time by simply unplugging the electric connector each side in turn. IIRC with the car jacked up and suspension fully dropped and under no load the compressor is run for 2 seconds. Using a jack the suspension is raised halfway to its normal position and the compressor run for 10 seconds. At this point WIS says to fully tighten bottom bolt of spring. The suspension is then fully dropped again and the compressor run again for 20 seconds. Then repeat for other side. This should get things near enough so that the car can be lowered onto its wheels and the self leveling will correct the levels when you start the car (if you don't have Star). In my case one side was a tad high and the other a tad low but overall pretty close.

One other thought is that maybe the pressure release valve on the compressor is partially open. Have you checked for air leaking at the compressor end. I have read that people jumper the compressor relay to run the compressor. This has the advantage (as when using Star) that the engine isn't running so you can hear whats going on. Finally WIS advises a new relay is installed as its likely the contacts are already damaged by the heavy load imposed on the system when a spring was leaking and the compressor was working overtime.

Hope this is of some help and good luck sorting it.


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[Nthkentman]

Thats correct yours (like mine) is quite a simple system.

MB are very clear, as are Bilstein and Arnott if you watch their installation videos on YouTube, that the air springs are inflated before the wheels are put on the ground and suspension fully loaded. This may be why your first new spring went bang.

I replaced both mine using Star and following WIS instructions. Inflating the springs is basically a six step process. 3 steps for each side with each side being done separately. Without Star I think you could do one side at a time by simply unplugging each side in turn. IIRC with the car jacked up and suspension fully dropped and under no load the compressor is run for 2 seconds. Using a jack the suspension is raised halfway to its normal position and the compressor run for 10 seconds. At this point WIS says to fully tighten bottom bolt of spring. The suspension is then fully dropped again and the compressor run again for 20 seconds. Then repeat for other side. This should get things near enough so that the car can be lowered onto its wheels and the self leveling will correct the levels when you start the car (if you don't have Star). In my case one side was a tad high and the other a tad low but overall pretty close.

One other thought is that maybe the pressure release valve on the compressor is partially open. Have you checked for air leaking at the compressor end. I have read that people jumper the compressor relay to run the compressor. This has the advantage (as when using Star) that the engine isn't running so you can hear whats going on. Finally WIS advises a new relay is installed as its likely the contacts are already damaged by the heavy load imposed on the system when a spring was leaking and the compressor was working overtime.

Hope this is of some help and good luck sorting it.


Hmm.... Food for thought... I will attempt the unplug a side at a time and the process for inflation etc. I wonder if when I replaced the piston seal on the compressor that I have made it worse. There doesn't seem a huge amount f pressure when I undid the link in the pipe under the back seat, When the compressor runs it doesn't have a lot or pressure. I can effectively plug it with my thumb, so perhaps it's the pump not delivering

 

[Borris1954]

OK it sounds like either your compressor is shot or the relay is providing a high resistance feed and thus making it feeble. The pressure in the system is high. I had one of my VOSS air connectors on the new Arnott springs pop out and it was one hell of a pop and rush of air! You could try bridging the relay and see what happens.

 

[Nthkentman]

OK it sounds like either your compressor is shot or the relay is providing a high resistance feed and thus making it feeble. The pressure in the system is high. I had one of my VOSS air connectors on the new Arnott springs pop out and it was one hell of a pop and rush of air! You could try bridging the relay and see what happens.

From what you say, I feel the compressor may be the issue... I can stop the airflow at the open pipe end with my thumb, but I can't see how the relay would change the pressure as the pump seems to be doing quite well, and after a few mins is warm, so it's running fine, just not producing air.... Time for a pump methinks...
I suppose I could replace the relay too.... If I can find it

 

[Borris1954]

Replacing the relay at the same time as the compressor is what MB recommend. I think a dodgy relay may still provide a voltage to the compressor but just not the full Monty rather like having a flat battery..

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[Nthkentman]

Replacing the relay at the same time as the compressor is what MB recommend. I think a dodgy relay may still provide a voltage to the compressor but just not the full Monty rather like having a flat battery..

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Good advice... Is the relay in the bonnet fuse and relay bank ?

 

[Borris1954]

From another thread on this forum "The relay for the compressor is in the fuse box under the bonnet. In my car its right at the back, closest to the windscreen and the outside of the car. Genuine mb ones are green and are about £13 from the dealer." See Still got issues on 2007 E class estate rear self levelling air suspension.

 

[Nthkentman]

From another thread on this forum "The relay for the compressor is in the fuse box under the bonnet. In my car its right at the back, closest to the windscreen and the outside of the car. Genuine mb ones are green and are about £13 from the dealer." See Still got issues on 2007 E class estate rear self levelling air suspension.

Thank you for all your assistance... I am purchasing a new unit c/w relay through Fleabay for £90, as I have decided that the OEM one is shot... It barely puts out enough air to inflate a balloon !.. So as I *really* need to get this car back on the road it's bite-the-bullet time and shell out. I'll take a look-see at the relay and see if anything is awry or if it smells "overcooked"... Thanks again... Will post results soon

 

[SteveK9]

Hope you've nailed it. Keep us posted.

 

[Nthkentman]

RESULT !
After checking the air pump for pressure, and discovering it wasn't able to even inflate a balloon, I purchased one from eBay, and tested it prior to installation. Talk about pressure !!...
So, fitted and working, car reaches the correct height, the suspension performs well (So far) and all seems to be in order.
Moral of the tale... Check the pump for pressure... 6-10 bar is the system norm, and a pump that won't inflate a balloon isn't going to push up a couple of tonne car !
Thanks to everyone who contributed and pointed me in directions for inspection and diagnosis

 

[SteveK9]

Well done that man, persistence has paid off.

 

[Borris1954]

Very pleased you have it resolved. Result!

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