W211 rear height sensor

[Manfriday]

Evening everyone, I'm hoping someone can point me in the right direction. I have owned the car for a little while and noticed the rear nearside dropped overnight! After a bit of forum searching, I accessed the suspension compressor. As luck would have it one of the 4mm pipes had been rubbing on a cable and sprang a leak, a ₤1.80 Norgren straight connector fixed it, happy days!! Now I have slightly disimilar heights on the rear of the car (about 20mm difference) and if I load the boot it doesn't raise back up. Any ideas? I have just ordered the iCarsoft V3.0 but just trying to get a steer before it turns up. THANKS. E320 cdi avantgarde 2003

 

[Wearsthefoxhat]

I have read that the system can be reset by touching the pos and neg battery leads together, however I am not sure if the aux battery needs to be disconnected or not before hand.
Not the best of help but another angle to look at..

 

[MJJ]

I have chased odd suspension performance on my '08 S211 over the last 18 months, including replacing leaking airbags and a worn compressor piston ring. Suggestions that may help in your scenario:
- I have found that the car does not instantly raise the ride height, even when the live data (on iCarSoft) from the height sensor clearly shows it is too low. I *think* it needs to be 25mm too low and for the car to be driving, before the system kicks the compressor in to raise the ride height.
- If you have had a leak for a while, the compressor may have been working overtime and has now worn its piston ring. There seems to be a max operation time for the compressor so if it is generating low pressure, it simply does not work long enough to build pressure, and raise the car. Strangely, my car needed to be about 40/50mm too low at the rear before any dash warning came up. Search for 'Bagpiping Andy' who does a great £25 kit with instructions to replace the compressor piston ring, 2 hours work.

Martin.

 

[Manfriday]

I have read that the system can be reset by touching the pos and neg battery leads together, however I am not sure if the aux battery needs to be disconnected or not before hand.
Not the best of help but another angle to look at..

Hi, thanks for replying. I also read that and had a glimmer of hope..........for ten minutes! Unfortunately, it didn't work for me, but always worth having a try!?

 

[Manfriday]

I have chased odd suspension performance on my '08 S211 over the last 18 months, including replacing leaking airbags and a worn compressor piston ring. Suggestions that may help in your scenario:
- I have found that the car does not instantly raise the ride height, even when the live data (on iCarSoft) from the height sensor clearly shows it is too low. I *think* it needs to be 25mm too low and for the car to be driving, before the system kicks the compressor in to raise the ride height.
- If you have had a leak for a while, the compressor may have been working overtime and has now worn its piston ring. There seems to be a max operation time for the compressor so if it is generating low pressure, it simply does not work long enough to build pressure, and raise the car. Strangely, my car needed to be about 40/50mm too low at the rear before any dash warning came up. Search for 'Bagpiping Andy' who does a great £25 kit with instructions to replace the compressor piston ring, 2 hours work.

Martin.

Hi Martin, thanks for the reply. I have just purchased the iCarsoft V3.0 and promptly plugged it in to get some info. Cracking bit of kit but scary seeing all the fault codes popping up!! I just need to fully understand how to use the iCarsoft. It did say that the level sensor wasn't operational and was showing an open circuit!? I decided to clear all the fault codes and start a fresh diagnostics read after taking the car out for a drive. Now it says that the compressor is possibly at fault (you may well be on to something) If I'm reading it correctly the car is 52mm low. I have tried manually inflating the bags via the iCarsoft and it activates the compressor for 40 seconds, but then says it was unable to inflate due to several possible problems, compressor, relay, level sensor, relief valve and leaks. Ha, where to start!? The joy of running old cars!!

 

[MJJ]

Hi Martin, thanks for the reply. I have just purchased the iCarsoft V3.0 and promptly plugged it in to get some info. Cracking bit of kit but scary seeing all the fault codes popping up!! I just need to fully understand how to use the iCarsoft. It did say that the level sensor wasn't operational and was showing an open circuit!? I decided to clear all the fault codes and start a fresh diagnostics read after taking the car out for a drive. Now it says that the compressor is possibly at fault (you may well be on to something) If I'm reading it correctly the car is 52mm low. I have tried manually inflating the bags via the iCarsoft and it activates the compressor for 40 seconds, but then says it was unable to inflate due to several possible problems, compressor, relay, level sensor, relief valve and leaks. Ha, where to start!? The joy of running old cars!!

Sounds very much like worn compressor piston ring to me. The fact that the compressor starts and runs for 40s, yet does not raise the car, points toward it generating very low pressure. If the compressor were working, but you had a small leak, it would raise the car to a level where it would subsequently sink from. If there was a valve stuck closed, I think the compressor would build pressure and cut-off long before the 40s. If the relief valve were stuck open, the car would be on its bump stops all the time.

Compressor is behind the front bumper, near side. You need to remove either the engine undertray, or the front half of the near side front wheel arch liner to get at it. If you can raise the front of the car a few inches at least, it is quite an easy job to remove it, fit the new piston ring, and reinstall.

Martin.

 

[Manfriday]

Sounds very much like worn compressor piston ring to me. The fact that the compressor starts and runs for 40s, yet does not raise the car, points toward it generating very low pressure. If the compressor were working, but you had a small leak, it would raise the car to a level where it would subsequently sink from. If there was a valve stuck closed, I think the compressor would build pressure and cut-off long before the 40s. If the relief valve were stuck open, the car would be on its bump stops all the time.

Compressor is behind the front bumper, near side. You need to remove either the engine undertray, or the front half of the near side front wheel arch liner to get at it. If you can raise the front of the car a few inches at least, it is quite an easy job to remove it, fit the new piston ring, and reinstall.

Martin.

Just an update, getting there but not 100% YET! Ordered the repair kit from Bagpipping Andy, striped out the compressor (just to make things worse, one of the legs for mounting the compressor has sheared off, should test my engineering skills) opened up the compressor and it is pretty scored up. I cleaned it up and fitted the repair kit anyway. It has fixed the issue, but I'm not convinced that it is working as well as it could. Air is almost definitely bypassing the piston ring. I have ordered a new Arnots compressor, a new filter, but I also need a new rubber jacket for it and I'm struggling to find one in the UK, other than MB main dealer. Looks like the general consensus is to also replace the relay? I would like to replace the rubber hose that feeds the compressor from the filter, but struggling to find that as well!? Do you know of any decent UK suppliers? Your help and suggestions have been brilliant and much appreciated. If you could do anything with the cold weather that would be a bonus? HA. Cheers

 

[Manfriday]

Sorry for the delays in responding to posts, just realised I had the wrong email in my settings! NO HOPE!?

 

[MJJ]

Just an update, getting there but not 100% YET! Ordered the repair kit from Bagpipping Andy, striped out the compressor (just to make things worse, one of the legs for mounting the compressor has sheared off, should test my engineering skills) opened up the compressor and it is pretty scored up. I cleaned it up and fitted the repair kit anyway. It has fixed the issue, but I'm not convinced that it is working as well as it could. Air is almost definitely bypassing the piston ring. I have ordered a new Arnots compressor, a new filter, but I also need a new rubber jacket for it and I'm struggling to find one in the UK, other than MB main dealer. Looks like the general consensus is to also replace the relay? I would like to replace the rubber hose that feeds the compressor from the filter, but struggling to find that as well!? Do you know of any decent UK suppliers? Your help and suggestions have been brilliant and much appreciated. If you could do anything with the cold weather that would be a bonus? HA. Cheers

Great news, sounds like progress. Regarding the rubber jacket, I don't recall my compressor having any sort of jacket on it so not quite sure what piece you mean. The compressor was mounted on rubber fixings as it obviously vibrates when operating, but these will be fitted to the new compressor.

Regarding the relay, I did not replace mine when fitting a new piston ring. However, I do recall it being stated as a warranty condition on new compressors so for piece of mind, it would be sensible to replace if you end up fitting the new Arnott unit. For the rubber hose, I imagine it will be very reasonable from Merecedes themselves - Mercedes Newcastle have a very active, reasonably priced and helpful eBay store and are always happy to be sent messages asking for prices on parts they don't actively have listed.

Martin.

 

[Manfriday]

Great news, sounds like progress. Regarding the rubber jacket, I don't recall my compressor having any sort of jacket on it so not quite sure what piece you mean. The compressor was mounted on rubber fixings as it obviously vibrates when operating, but these will be fitted to the new compressor.

Regarding the relay, I did not replace mine when fitting a new piston ring. However, I do recall it being stated as a warranty condition on new compressors so for piece of mind, it would be sensible to replace if you end up fitting the new Arnott unit. For the rubber hose, I imagine it will be very reasonable from Merecedes themselves - Mercedes Newcastle have a very active, reasonably priced and helpful eBay store and are always happy to be sent messages asking for prices on parts they don't actively have listed.

Martin.

Yep, good call about MB main dealer, I'd be a fool if I didn't check! The jacket is for the small Air filter, but again I'll Ask MB. Just waiting for a new ball joint splitter to turn up now and then I can move on to the next job.