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viscous fan

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Ballybarney View Drop Down
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    Posted: 08-August-2015 at 19:45
Hi lads I am looking for your option on my 1992 318i viscous fan my query is that the viscous fan comes on when I start car from cold and cuts out when car warms up to normal spin the temp holds at half way no over heating problems just thought the fan would only come on when car is hot???cheers.
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Andrew Rolland View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Andrew Rolland Quote  Post ReplyReply Direct Link To This Post Posted: 10-August-2015 at 08:43
You are right, it should only come on when hot. 
 
By its nature a viscous fan only works when its hot and not when its cold.  It will always spin with the engine.  When cold the fan viscous clutch slips and the fan does not rotate quickly.  When the engine gets hot the viscous clutch does not slip thus the fan blades spin faster.  You can hear the fan kick in with a growl/roar as you increase the revs above idle.
 
With the car stone cold and the engine off, spin the blades of the viscous fan.  These should be stiff to push and uniform in resistance.  If it spins easily then you have most likely have lost your fluid and it needs replacing.
 
An electric fan may kick in when the engine is cold if it has a faulty control unit.  A viscous fan can never kick in when the engine is running.
 
But the important thing is that your car is not overheating.  The minute that the temp gauge goes beyond normal switch off.
 
My E39 had a viscous fan and in the three years I had it I only heard in kick in three times.  Newer cars don't have them as they are seen as heavy and energy sapping in todays tree hugging emission dictating days of motoring.....
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Ballybarney View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ballybarney Quote  Post ReplyReply Direct Link To This Post Posted: 11-August-2015 at 20:04
thanks man for your reply,now the reason that I asked the question it that I have just put on a new one and never notice how the old one worked it just turned very freely when cold  so I decided to have it replaced to be safe now when I start the car it comes on like a aeroplane?cheers
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