1997 BMW 328 thermostat

Here is an exploded view of the T-stat and water pump. The fan and the shroud need to be removed first, then the bolts can be accessed. The fan can be removed with a thin 36mm open end wrench and it is a left hand thread. The plastic buttons that hold the shroud often break and I usually replace them with plastic zip ties. I recommend replacement of the water pump if it's age is unknown and for preventive maintenance.