How easy should the viscous fan be to turn with a cold engine?
I know this will be subjective but I recon that mine is too stiff and is dragged round at belt speed with a cold engine - it certainly shifts some air from the get go..

The only viscous fan I've see Is what is fitted on my D1 and when cold and it won't spin, but when trying, it will turn just the with of one blade and the stop which is as it should be.
When cold the fan sounds like a turbine untill the viscous fluid has circulated and then the fan gets quieter and after driven 100 yards or so down the road, on my disco the turbine sound returns when the engine is hot and its a hot summers day and in traffic when the fan locks up fully.

On initial cold start the fan is stiff untill the fluid will start making it's job in it(few minutes) then you must be able to stop it with a rolled newspaper with engine running untill the thermostat opens then it's bimetalic valve will start acting and the hottest the radiator becomes the stiffest the fan should be, that's how it works... if you can't stop it while the gauge didnt reach the middle it's stuck and that will lead to prolonged warming up of the engine

Cheers for the info chaps. I didn't realise that the fluid had to circulate before slip was allowed. I will try the rolled newspaper pokage later and see if it really is too stiff or OK.

Matt