The crank sensor (and coolant tubes) pairs nicely with changing the starter. I have 500k km on mine so you probably have some good use left! Some on this forum have just done a clean-up on the starter and have had good success getting the cranking speed back.

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1988 325is (purchased new) sold
2004 X5 3.0 2005 X3 2.5
2008 X5 3.0 (new to me)