WARNING: This page is about a different car, the 2003 BMW Z8, 2002 BMW Z8, 2001 BMW Z8, and 2000 BMW Z8. However, it is still accessible from the selected car via links, so may be relevant.
TIGHTENING TORQUE SPECIFICATIONS (FAN)
Type
Thread
Tightening specification
Measure
1AZ Fan clutch on water pump Coupling nut (left-hand threads)