E53 Electronic Height Control

[2mbb]

Hi: I'm trying to get some more information to help trouble shoot an issue I'm having with the electronic height control (EHC) on my 2001 X5. I have the air springs on the rear axle. My condition is that both air spring over fill to the point that the vehicle ride because very rough. It is also very noticeable that the rear is much higher than the front (stink bug stance). I can't find much in my Bentley manual about how this system works, but in the trouble shooting table, it suggests fixes to this problem are: The EHC control module is in transport mode (this is used by BMW at the factory and during transportation to the dealer--I'm not sure why it would suddenly be in this mode now after 20 years), replace the air compressor, and blow out clogged air lines.

The latter I can do, but if that doesn't work, I'm reluctant to replace the whole air compressor, "just to see". I have loosened/removed the air lines going to the air reservoirs to bleed the air from the air springs, and the systems then seems to work OK for a while, but after a couple of trips, the air spring are over full again. The warning message is a little sporadic. I have gotten the message from time to time (and I'm not the primary driver of this vehicle, so I don't know exactly how often) but it usually goes away and the message is not showing when the air spring are over full. I don't return any relevant codes with the scanners that I have.

Does anyone have any other suggestions how to troubleshoot this issue? I would suspect the drain valve (9), but I'm not even sure how it works as I don't see a vent to atmosphere any place. But I don't really understand the various schematics for the valves 7, 9 and 10.

Thanks.