The fan drive coupling is secured to the water pump by a left-hand threaded connection. When removing it, be careful not to damage the radiator fins.
1. Remove the fan shroud if necessary.
2. Holding the pulley from turning with tool No.11 5 050, loosen the union nut of the water pump shaft using special key No.11 5 040 and remove the impeller with the fan drive clutch from the pump.
Left-hand thread nut.
3. Unscrew the bolts and separate the impeller from the coupling. When installing, tighten the impeller mounting bolts with key No.11 5 040.
When tightening bolts using a No.11 5 040 wrench, a reading of 30 Nm on the torque wrench corresponds to 40 Nm of actual tightening force.
[This publication was borrowed from an online resource BMWMAN.RU]