Viscous Fan

amcdonald

Active Member
Hello

I have the mysterious (to me) viscous fan on my NADA. The engine is off at Aluminum V8 for a redo and it’s threatening to make a reappearance here in Cal, but I came upon the fan when tarting up my ancillaries. The fan rotated pretty freely, which I gather is not ideal but then how free is free? Before the engine was removed, on the few and far between runs I don’t recall overheating so there’s no alarm bells there but I am worried the coupling is duff. Any suggestions? I really don’t want to be disassembling after I get the motor back in.

I get the feeling this is a stupid question but I am just not sure why yet.....but, can I just finagle the plastic fan with a permanent connection to the pump screw and forget about the clutch mullarkey entirely?

Cheers
Adrian
 
I have a viscous fan too.
Mine runs free to turn by hand too. Im sure theyre only buggered when they are bound up and turn as one . ie pump and viscous coupling.
 
My understanding is that they turn freely to allow more power to be available and only "kick in" when
the conditions require them.
For my Land Rover, I was advised to drive it to the point where the fan is engaged, then try to stop the fan at idle with a rolled up newspaper. If it stops, its faulty.
 
Hello

I have the mysterious (to me) viscous fan on my NADA. The engine is off at Aluminum V8 for a redo and it’s threatening to make a reappearance here in Cal, but I came upon the fan when tarting up my ancillaries. The fan rotated pretty freely, which I gather is not ideal but then how free is free? Before the engine was removed, on the few and far between runs I don’t recall overheating so there’s no alarm bells there but I am worried the coupling is duff. Any suggestions? I really don’t want to be disassembling after I get the motor back in.

I get the feeling this is a stupid question but I am just not sure why yet.....but, can I just finagle the plastic fan with a permanent connection to the pump screw and forget about the clutch mullarkey entirely?

Cheers
Adrian
The viscous fans do rotate freely by hand, I think you will find all is well. It may pay to check the water pump bearing for smooth running and for leakage underneath up inside the pulley whilst it is off the car.
 
I get the feeling this is a stupid question but I am just not sure why yet.....but, can I just finagle the plastic fan with a permanent connection to the pump screw and forget about the clutch mullarkey entirely?

Hi Adrian,

The 13 bladed nylon fan with viscous coupling were fitted as standard equipment to Rovers that were exported to 'hot' countries and locations. Australia, Middle East, Africa, Cyprus, Portugal, and New Zealand all received such cars.

I advise most strongly not to attempt to fit the 13 bladed fan without the viscous coupling. Use and enjoy the benefit of using them as they were designed, which is vastly superior to a fixed fan arrangement. Mind you, you will also need the correct water pump as the two pumps for their respective fans are not the same.

Ron.
 
I think we need to clarify that this certain type of viscous is of the "slipping type", i.e. it follows the speed of the engine at low rpm, but after a certain point in the rev range that the load starts to exceed the internal friction of the viscous unit, it starts to slip, which means that it doesn't rotate at the same rpm with the water pump in order to not sap unnecessary power.

This type of coupling was superseded later with the more common type that does not transfer any motion when cold, but it starts lock up when it senses heat.

Of course these two types should be treated in a completely different way when testing for good operation.
 
Okay, sort of kinda what I thought about connecting the fairly honking fan directly. So let’s not do that.

I will check the water pump but it’s the same unit as came off and in great shape so just new gasket and shiny screws.

I think I am suffering from the expectation that absolutely nothing on the car will still be working. It’s induced by living in SoCal and driving a British motor and hearing the laughter when I claim my Lucas electricals have never been a problem.

So, i am gonna think it’s perfectly fine. Just like my Lucas bits.......
 
I'll send you some positive vibes, should take care of the fan and the electrics.......




















Well the fan anyway.
 
Thanks. Now I brought up the Lucas topic, that’s probably now all buggered too.

PS. Edit: Of course I meant DandD fabrications, 215 V8 specialists. Before anyone looks for the (non existent) “Aluminum V8” shop I mentioned. That’s their web site address.
 
Here is what the Discovery fan and viscous looks like...
Front
0DCWYt0.jpg

Rear
MkfWtNn.jpg

Note that the rear is attached to the water pump nose via a LH thread female - same as SD1 IIRC. I adapted the unit to another car by cutting the male LH thread off a dead Disco water pump and pressing it onto another shaft. If you have economic access to the parts it would be an easy conversion for a P6B, although an electric fan set up might be cheaper. Note that these fans are prone to crack and break up when worked hard in hot climes - getting very messy ! From outside the car you can easily hear when the viscous tightens and drives.
 
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This type of coupling was superseded later with the more common type that does not transfer any motion when cold, but it starts lock up when it senses heat.

Of course these two types should be treated in a completely different way when testing for good operation.
Then I was in Fort Worth Tx a few years ago I had the loan of a LR Discovery 3 ( LR3) V8 petrol whilst some work was being done on my V6 Diesel version. the ambient temp was about 35 C . Every time I stopped at the traffic lights so no air flow through the radiator, one could hear roar of the air movement as the viscos fan was cut in. About 100 yards down the road it would stop until the next set of lights . This type of fan will usually stay locked on initial start up as the fluid inside gets circulating and then will cut out until needed. Interestingly my Diesel version hardly ever cut in at all but they tend to run cooler than petrol's.
 
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