I have been now a owner of my 2004 X5 for two months. It had one rear airbag blowed when I have bought it, for the first thing I have replaced both rear air shocks (bilstein) with new ones. But still the driver side will deflate over night! For some period it was not deflating, but now it is again defleating. Some times it seems that it leaks more than the other day, in some random time period everything is ok, last time I did not notice any change over night fo 6 days and just suddenly the problem was back! It seems that both sides are leaking, but the driver side is leaking more.

I have been by the local car service for several times and we have searched desperately for some air leaks with soapy water, but we have not been able to identify any leak anywhere.

Can the compressor solenoid valves somehow leak? How could this be checked? Are there any other factors what can cause the deflating?