1991 W126 Fan Clutch

Hi All,

I need to remove my fan clutch. I have done it on the older engine, but never on the newer. It seems to be bolted in by a center bolt, rather than the prior 4 bolt arrangement that mounted the clutch to the shaft.

I am not at the car and need to have all my tools ready - can anyone tell me what size nut it is or is it a special star or other pattern?

Thanks,
Richard