Many thanks for the reply and the heads up on those items. The expansion tank failure is also something common to the E31, E31 and E34 cars, so I guess it could be deemed a general BMW thing. I will add that to my hit list as I am not sure when it was last replaced. I had planned on getting new belts and replacing them - cheap insurance. Thankfully I have a very good friend who owns a tranmission shop but still is never a cheap endeavour when digging into them.

Regarding the level sensors, my X5 only has the rear self levelling, and according to RealOEM there is only one. Does that make sense to you (given that you said you have replaced all 4 in yours)? Or is it just the X5's with the four corner air suspension that have one on each corner?

Again, thanks for the guidance.

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Mechanical Children
2001 BMW X5 (4.4, sport pkg)
1991 BMW 850i
1992 BMW 525i turbo
1992 BMW M5
1992 BMW 750il CSI
1997 BMW 528i
2001 BMW 540i touring
1991 Alpina B10 3.5
1991 Alpina B10 Biturbo
1991 Alpina B12 5.0 (E32)
1992 Mercedes 600sel
1993 Mercedes s600 Lorinser
2002 Ford Excursion 7.3
2003 Jetta TDI