How do you install the fan & pully on an alternator???
 

RE: a 1985 300 TDT (or any other car for that matter). Removing the fan & pully from the old alternator is easy - impact/air gun - short trigger-pull and the nut's off. How are you supposed to tighten the nut holding the same fan and pully to 70Nm?? Actually, how are you supposed to tighten the fan and pully at all? Obviously the whole assembly just spins both directions with no resistance. There's only the threaded stud and a nut. Nothing to hold onto to torque it. You CANNOT put something in the blades of the fan to hold it steady (like a screwdriver), the blades will bend - guaranteed.

Use the same impact wrench, At least that is what I did on my daughters 240D.

Dave

Tighten the nut hand tight then reinstall the alternator and drive belt. Press on the drive belt to hold the pulley and torque the nut to 70nm.

I didn't think of that.

If you go with the impact wrench to tighten the bolt, try to reduce the torque. Napa just changed a pulley for me and broke the hole out with excessive force. One possibility is to adjust the impact wrench torque off line and check with a torque wrench. The orginal Mercedes pulley was very weak around the bolt hole. The pulley that came with the rebuilt was very substantial although a little smaller than the original. Still worked ok within the range of the belt, spring and shock. This on a 87 300dt.