Suspension dropping one side

[Huxley06]

So I have a problem that I need some help with. (E70 4.0d 2011)
The rear drivers side drops on its own after a couple of hours. I have put a new bag on the passenger side last October and a new one on the drivers side (thinking it was the culprit) yesterday (sat 01/05/21) No drama’s and I have used arnot bags for both sides which are as good I’m told as the originals. So 2 hrs later I noticed it had dropped again. I took the under tray off again and sprayed all the joints/fittings with soapy water to look for any leaks... also the blue and red lines where I could get to. I’m convinced that I don’t have a leak, ....... however looking at the self leveling units attached to the rear beam and suspension, I can see one of them is maybe broken and corroded a little, and with the engine running if I grab it and give it a very little wiggle the suspension goes up. Likewise with the engine off, a little wiggle and it goes down......I’m reckoning at this point, that one maybe two sensors could be the culprit(s)? and not the actual air system itself?? My thought is, looking at the damaged/wear n tear bit, it could be out of sorts to its correct setting (if that makes sense)
Any advice before I speak to the Indy on Tuesday?

[Leslie]

Hi I take it you have leak checked at the little olive into the bag as that's the most likely place for a leak as they can split if overtightened after a bag is changed , or it at the compressor if that's where you took a line of to deflate the bag for removal ? Arnott are good quality bags and it sounds like the sensor is working for now even if its looking bad , I think with those they can be swapped side to side to see if the fault moves with it .

[Huxley06]

You can’t check the connection to the bag once it’s inflated. I was as careful as I was when I did the other side and did nothing different in doing the second one yesterday. That’s interesting that I may be able to swap them over? I didn’t want to un clip the power to them in case it threw a light on the dash. If I can unplug and swap them without an issue then I will try that in the morning... more googling to do it seems.

[Alan Gunn]

Just changed one of the sensors on my e53 and didn't get a genuine on but it works ok and for a lot less money.
As above they will work on both sides even tho realoem shows 2 part numbers they are not sided.
Swopping them to see if the problem moves might be tricky as i had to cut one bolt off when i did mine didn't want to come off easy.
Just had a look at the one i got and it is the same part as yours fits all the X range i think well the older ones.
https://www.ebay.co.uk/itm/153739581109 ... SwQXZd3V3N

[Huxley06]

Cheers for that. However this morning I decided to take the new bag off and check the pipe connection again. As the bag was flat and there is no way I could check for a leak with it in my hand I decided to undo it and use a small amount of liquid ptfe that I use for central heating radiators. I also sprayed around the compressor block but could not see anything. I then started to undo the 4 torx screws that hold the block together. After I removed 3 of the 4 as I started on the 4th screw, air started to come out, I guess from the near side red tube which was still under pressure! I had visions of the block flying apart and little parts shooting everywhere, rendering it no longer useable. So I Put it back together, started the car and it has not dropped all day.
I guess, I can safely put this down to the bag to blue line connection weeping slightly as I could not hear air escaping with my ear as close to it as possible with the wheel removed.
Hopefully this will help someone else when they google my problem.