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retro-fiiting a viscous fan

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After a bit of advice regarding viscous fans, I've seen lots of threads saying about the removal of the fans but none about actually re-fitting a new one, well to me anyway. I've absoutley no idea about them, I know how they work in theory, but don't really have any practical experience with them.

From what I can gather, they appear to fit on a threaded bar on the end of the water pump? There seems to be various types of (3.5 V8) water pumps, some which allow for fan fitting, others which don't. Unfortunately i'm not around the car at the moment, but if for instance my water pump did not allow for fitting of a fan, I assume the only way to rectify this would be to change the entire water pump?

So, assuming what I have got so far is correct, what is the actual part that I require. Is is a case of simply threading something on such as :


And then, job sorted? I assume not, as that seems far to simple!

Input very much welcome.

Further more, another thread I have running here;



Basically, I have a V8, series rad, and electric fan infront of rad pushing air through.. I can just about squeeze a electric fan behind the rad to pull air though, but I'm also thinking I could maybe get a viscous fan in there and shift a hell of a lot more air!

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As I read your first paragraphs, I was going to ask if it was a Series vehicle retrofit, but you soon made that clear.

Viscous fans are far superior to electric, and most people removing them from a standard vehicle do so because they have fallen for the fraudulent claims by the electric fan companies about improved performance and economy, or the misperception that en electric fan will improve warm up times in cold conditions.

It is a different story with modified vehicles. With engine retrofits, there is often insufficient space for the viscous fan, or the water pump (or other fan shaft) is in an unsuitable location for the older engine bay and radiator. As much as I hate electric fans, I had to use one for my 109 Tdi retrofit as the Discovery version of the 200Tdi puts the fan too low and too far forwards, severely overlapping the chassis cross member and nearly in contact with it. It looks to me like you would have similar problems.

As long as you have a decent sized fan, a reliable thermostatic switch and a manual override switch to pre-emptively activate the fan (before a long, slow climb, for example) and to act as a back up if the thermostatic switch fails, then you should be fine. Many production vehicles have electric fans because of similar considerations. It is just a matter of realising the viscous fan is preferable where practical, the electric fan merely an acceptable alternative where a viscous fan won't fit.

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Managed to have a look this morning, under the rubber capping was a thread as shown below...Yay...

So one presumes I can 'just' put one on..


In terms of finding one to fit, do I need to get one specifically for a 3.5 on carbs, or will any for a RV8 (3.9 etc..) fit if anyone knows..

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If it fails, it doesn't lock up, meaning you don't get the properly cooling as the fan almost freewheels...

You will need to look at cowling, without this you will have a VERY inefficient fan set up.

I'm pretty doubtful about it fitting with any degree of ease though.

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They can fail open or closed - open means the fan still idles through residual friction instead of being locked to the shaft. Failing closed means they're locked even when cold. The penalty there is small. If it fails open, then you can use a couple of cable ties to lock the fan to the hub. It's always worth having a few cable ties in the car for securing wiring, hoses or other items that come loose anyway. I have had two viscous hubs fail, and both failed closed. It's not a big deal - they're far more reliable than electric fans, and easy to check; they should have a bit of resistance when cold, but be easy to turn by hand (or stop with the aid of a tool, not fingers, when running cold), and should be ocked up when the engine is up to temperature.

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