Why are you thinking that there is a problem with the fan? Having a boil over after hot soak at 100c isn't the fan's fault. If the coolant was even close to being strong enough it would not boil at 100c even if the pressure wasn't holding.

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