I have a Merc E220 - W124 - 1995 Sportline

I have had cooling problems and found the Fan Viscous Clutch is shot (I have repaired a similar animal on my Opel Record), but cannot see how this darned thing on the Merc comes off.

There is a large Hex nut about 30 mm across flats which seems to couple it to the water pump pulley (shaft ?) and 4 x 10 mm round hex socket studs fixing into the same pulley. They sit closely around the large nut.

Does the large nut, screw the VFC onto the pump pulley shaft, or is it fastened by the 4 studs. I am shy of wrenching the large nut in case it is not supposed to turn, and shy of removing the 4 x studs for if the pulley falls off.

If you are interested I can tell how to fix the viscous clutch very simply to make it work same as normal without the bi-metal strip.
(this is a little lengthy for this message)

Regards - John Clarke