Meanwhile the OP has added antifreeze to his X5 and is sitting at his computer wondering what the hell did I start with my question.

Parts break, to some more than others. Next posting! My expansion tank is still happy at 10 years. I worry more about plastics that are not UV or ozone proof. Then I am one of those types like many of us, who washes and sprays protectorates on my CV boots to extend their lives from parking turns, changes the oil annually and all the filters, etc........

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2005 X5 4.8IS
The Blue ones are always FASTER....

Current Garage:
2005 X5 4.8is
2002 M5 TiSilver
2003 525iT
1998 528i
Former Garage Stable Highlights
2004 325XiT Sport
1973 De Tomaso Pantera, L Model
1970 Dodge Challenger T/A 4 sp Alpine White
1970 Dodge Challenger T/A 4 sp GoManGo Green
1971 Dart Sport, “Dart Light” package
1969 Road Runner 383
1968 Ply Barracuda 340S FB Sea-foam Green