Yes thanks Jim, I found your mod. from a search on "viscous fan". earlier in the week.....however ... have to get the durned thing off first Jim.......they do things differantly in Africa it seems.......a recky at sparrow (whilst being watched by a long crested Eagle) revealed no bolt , just the control rod behind the bi-metal slap in the middle.
So it has to be the large nut sitting between the pump boss and the clutch about 25 mm across flats that screws on the pump shaft. No shaft to be seen, just the large nut. Makes life easier as it has the engine to turn against. Will update (with bruised hands) on progress Monday. I suspect this animal maybe a beastie from the succeeding "C" class ????