The water pump fails around 100k, its more due to hours not miles, its electric and not driven by a belt.
Pump should be $450 thermostat $150, maybe 2 hours of labor at a good indy bmw shop.
Order from (East Coast) getbmwparts.com or bmwpartspros.com (West Coast)
Gotta pay to play.
WTB LUX 5.0+