2003 S211 down on its knees (again)

[ksareen]

Hi,

After 3 years of replacing the N/S Rear Airspring, my 2003 S211 E220 CDI has got the issue of both rear airs prings going down this time. Thankfully, this car only have air springs at the back!

It started with an airport run a few months month ago where I put lots of luggage in the boot along with luggage in a roof box.

The car was quite low (wheels inside the arch) when I reached airport but lifted up after removing the luggage with the engine/air pump running. Upon the returning to collect the car a week later, the car was down again in the parking lot and since then, the car goes down (both rear wheels) in 2 scenarios:
1. If there are heavyish people sat in the back of car (its a 7 seat model)
2. If the car is left un-used for 4-5 days.

Since both of airsprings go down now (instead of one last time), I am thinking its some kind of valve failure or pump? Are both airsprings known to fail at the same time?

A thing worth mentioning is, I hear lots of hissing noise at the N/S Front wheel arch after I come back from a drive, I used to think this was to release excess air pressure from the system.
Is this where the air pump is? Could there be a leak here?

Please just ask if I need to provide any pictures.

Any help/ check/ feedback is highly appreciated as always.

 

[LostKiwi]

The hissing does suggest a leak and is most likely the cause of your problem I would say.

 

[ksareen]

Hi LostKiwi, thanks for your reply. I really hope that is correct as air springs aren't cheap, especially hard purchase to justify with the age of car!
Any ideas where to start looking? Am I right about the location of air pump (N/S/F wheel arch) and should I strip that area first to start looking?

 

[V6Matty]

IIRC there more likely to leak from the t-bar near the rear axle,

 

[malcolm E53 AMG]

Does sound like a leak

I would imagine you are correct with the situation of the air pump and the valve block location.

Take the wheel arch liner out to expose both and use soapy water to look for leaks. If the pump is original it may be due for replacement or you may have valve block problems, look for corrosion at the pipe connections. If all appears well track the air pipes back to the rear axle and check for leaks there as both rear airbags are dropping it doesn't appear the problem is with either of them

Good luck with it!

 

[ksareen]

So I removed the wheel arch and the air pump. A rubber hose coming out of air filter had a cut near the clip, so cut off the bad/ older section of pipe and installed the pipe again.
Funny thing is if I move the pump about when its running, I can hear an air leak, but cannot work out where its coming from, been spraying soapy water all over the pump.
Another thing is the rear wheels have not gone down since the pump was removed, so there must be a no-return valve somewhere that is holding the pressure for the rear air springs.
My feeling is there might be a leak in that area. Can someone please point me to the layout of the pipes going to the rear springs?

"more likely to leak from the t-bar near the rear axle,"
Where is this t-bar? Is this a valve?

 

[malcolm E53 AMG]

I would imagine the valve block is holding the air pressure to the rear airbags. Now you've found and removed a piece of rotted pipe from the pump better to try the car and see where you are now with it now, it might have sorted things out

 

[ksareen]

Hi Malcolm, the rotted pipe is the intake pipe to the pump, so it can't relate to the pressurised leak IMO.
I am willing to check the valve block that holds the air pressure before I put the car back together.
Tomorrow I will lift the rear of car, so any pointers towards its location + anything else worth checking would be great to know.
Thanks

 

[malcolm E53 AMG]

Might be worth reading this guide:

http://www.mercedesmedic.com/air-suspension-troubleshooting-airmatic-visit-workshop/

All the components are mentioned so hopefully it will prove helpful, there are also some good videos on Utube re the valve block etc, there is a link for this in the link script

 

[Ian Parkin]

Here's what i found after similar problems on my 04 s211 estate with 142,000 on it
I posted a request for help on here but no-one replied..maybe no-one knows how the system works properly
One side suddenly started going down after about 30 mins and overnight was on the bump stops the other side stayed up longer but in 2 days was completely down.
Before this it was always up to correct level and raised and lowered as required by the load in the boot.

I broke into the pipe under the rear seat on the near side and installed a t junction and pressure gauge reading max of 160 psi
Started the pump manually on the relay and pressure went up to 160 + pressure gauge now useless...bought 300psi gauge and retested pressure would go to 250 easily and stay there for days
So i was sure that pump was good
Then broke into wiring in offside rear seat area and tested wires going to valve onto top of the air struts...applied 12v and the side would go down.
Tested for each side
If pump started manually and valve opened the side would go up very slowly.

So i was now sure that the leak was on the strut so bought 2 new struts £366 each exchange from local mb dealer or 360 for a pair of arnutt struts on ebay
On receiving the struts they look very well made but they are open at the top...no air connector or wiring connector you need to remove that from original units..
Removing struts is quite easy..old struts very rusty and had to drill out screws holding tops on to remove solonoid valve from the top of the strut.
All told it took about 3 hours to do both sides...
Then pumped up both sides with my shop compressor to 150 psi by opening valves manually with 12v
Then connected everything back up and so far works fine and stays up fine

The thing that threw me was that both struts had sprung leaks within days of each other after 13 years and 140k miles

Leaks on any the pipe work shouldn't let the system go down when at rest as the struts have a valve in the top so is sealed when ignition off
It could be conceivable that there could be a leak at the o ring where the valve goes on the struts but unlikely

If you have a leak in the strut then no amount of soapy water will show you on the car as the harder plastic concertina hides the rubber bladders and you cant remove it in situ.

Also the pump will only run for so long if you have a leak to protect it from running constantly this is controlled from the controller box.
Also the ride height is set by the arm length from the roll bar to the sensor...the bracket that holds the arm sits on a flat on the roll bar so you cant adjust there if you wanted to
You can lift the system on star and let it down but there's no facility to make it sit higher in normal use

Hope this helps anyone trouble shooting this system

 

[ksareen]

Leaks on any the pipe work shouldn't let the system go down when at rest as the struts have a valve in the top so is sealed when ignition off
It could be conceivable that there could be a leak at the o ring where the valve goes on the struts but unlikely

Thanks for a very helpful reply Ian. Could you please share some pics on where the valve is and how it looks? A pointer to the O-ring would be super great!
With the car over 200K miles, I am not keen to spend a lot on it. If the struts are gone again, I would rather sell it and move on.

 

[Ian Parkin]

Well the valve fits in the top of the strut under a cover plate which then has a hole in it which locates in the body shell of the car
I haven't got any pics as its all on the car
The strut bolts onto the wishbones at the bottom and just locates at the top on a little plastic peg which screws onto a stud on the body so when the strut is under slight pressure it locates properly
When you remove the solonoid you will see the oring either in the hole or on the solonoid spigot

As i said its very unlikely that it will be leaking from the o ring....and as an aside you have to completely remove the strut to get to it so if you are doing all that you may as well get new struts as if they are anything like mine the cover plate screws need drilling out as they were really rusty...maybe genuine struts come with the valve already in situ

 

[ksareen]

Thanks Ian,
Since I fitted the compressor back at front, the car is not lifting to its original position. It goes slightly above the half way mark (top of wheel almost matching the wheel arch), then I can hear the compressor at front releasing air and the car at back goes down a bit.
Then it seems to stay there but I am not sure whats going on. Maybe removing the compressor was a bad idea!

Update: I've found a major leak at the small white plastic pipe carrying high pressure air from pump to the rear springs. This was caused by the pipe rubbing a set of wires that had come loose from the pump. How do I fix this? Any special adhesive?

Ian, how did you connect the plastic pipe again after removing the T-Junction where you connected the pressure gauge?

 

[Ian Parkin]

You can get a small length of pipe (4mm od )from an industrial air control co and 2 inline connectors to repair it. I dont think you will have any luck repairing a hole with adhesive as it contains 250psi at times...
Having read though what you have written if the car sinks over time when stood its got to be the struts leaking as the pipe work is under no pressure when stood
Certainly though you should not be hearing air escape at any time from anywhere on the system as even when the car is lowering itself because of the load being removed its so slow you wouldn't hear air escaping

 

[ksareen]

Hi Ian,
Many thanks for your reply. I've ordered a 4mm 26 bar long sleeve compressed pneumatic connector to repair this leak.

I agree that pipework is under no pressure when the compressor is ON, so I may have a problem with the air springs as you suggested.

Would you know if the rear air springs have reservoirs and/ or level sensors on these estates? If yes, any idea where they are located?

I am going to deal with 1 issue at a time, so let me get this repaired and I will get back with further observations.

Thanks for your help and patience once again.

 

[Ian Parkin]

read my post no 10 for as full an explaination of how the system works as i can manage from reverse engineering it

 

[Ian Parkin]

heres some photos of an original strut but without the solonoid valve