2018 740e xDrive iPerformance
As Robin750 mentioned- The first thing (and cheapest) is to check for leaks. I would spray soapy water on all the valve block connections, the air line at the rear passenger strut, and the two accumulator connections (at the accumulators if you can gain access to them). While looking at the valve block (before spraying it with soapy water) look at the electrical connections and you may even want to unplug all of them (one at a time) to make sure there is no water in the electrical connections and they look clean. You might need to clear an error or two if unplugging.Last night I scanned for codes and got the following:
482974 VDP: Vehicle level - not adjustable
482963 VDP: Compressor relay - maximum switched-on period exceeded
483103 VDP: Vehicle extremely low - rear right
482953 VDP: Solenoid valve, pressure accumulator - maximum switched-on period exceeded
482936 VDP: Solenoid valve - rear right - maximum switched-on period exceeded
And like I mentioned in another post above, there are 4 to 5 bursts of air lasting ~2 seconds from the rear right wheel area after I turn off the car. I do not hear this from the front right wheel.
Does this still sound like it could be a valve block issue as suggested above?
There is a very particular set of events that would have to happen (electrically) at the sane time to get the sudden release of air pressure out to atmosphere from one strut. For example, Three different solenoid valves all have to open at the same time- #1 Electrical solenoid valve for rear right air suspension strut (this one is normally closed and is in the valve block) #2 Electrical drain solenoid valve (this one is normally closed also, but is in the compressor body) and #3 Pneumatic discharge valve with pressure relief function (this is a pneumatically controlled valve controlled by #2, and is normally a flow control slow release, but when activated by #2, vents to atmosphere very quickly, also in the compressor body).
The only reason I could see the VDP causing this would be if it thinks that ride height sensor is fully extended, and tried to release pressure on that strut, but normally it would use the slow release to drain the pressure slowly, unless- the pressure sensor in the valve block is bad or has a bad electrical connection, and therefore can't verify the accumulator pressure. The compressor normally runs while driving and fills the accumulators (and can fill the struts directly), but when the car is off the compressor does not turn on unless the car is in the "Awake" condition when the car sees a remote and you see some message in the center display. When in this condition you might hear the compressor running if you put your ear near the rear drivers side wheel well.
I think you can look at the raw data from the ride height sensors using ISTA, but I have not tried that. Robin750 may know more about how to do that. I doubt the ride height sensor is the problem though, because you would have a similar air loss problem while driving.
You might also be able to see the data from the pressure sensor in the valve block somehow to see what the pressure is doing.
I also am not sure why (after the initial drop of the rear passenger side), the front passenger side would drop down slowly as well, since they don't share valves or air lines. Unless you park on a sideways slope maybe? Then the car would try to level itself and drain air out of that strut if the rear was already low.
This document has a good explanation of the air ride suspension starting on page 20-
3.1 MB Views: 89