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Viscous V's thermostatic fan

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As the title really, after having a think that my 90's cooling isn't as great as it could be what would people recconend? Replacing the viscous centre part with a genuine new one, or would people go down the thermostatic fan route??

Any one fancy sharing an opinion or experience ?

Also where people have bought from links would be useful ?



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Difficult one to answer really. Viscous coupling nomally either siezes solid or freewheels. One improves the cooling so much that it struggles to warm up, and the other does nothing.

Only real benefit from electric is slightly shorter warmup time. Having used them on a few vehicles I can honestly say that I have NOT noticed any improvement in power, OR fuel consumption, If there is, then its marginal IMO

They dont like being dunked either.

Overall, I would say that if the Landie is used mostly on the road with very little or no SERIOUS offroading, then go electric if you want to, but if its a proper offroader, stay with the viscous, as its more reliable and far more powerful when needed.

I would look at your radiator first though. Caked in mud ? Fins rotting and missing ?

Maybe a chemical flush if the coolant is suspect

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I'll echo what Maverik says firts

I as most of you know run a 300Tdi Defender station wagon. My expedition motor.

I run a Kenlowe electric fan, The switch is in the thermostat elbow that Land Rover use for their fan switches. The actual fan is very close to the radiator matrix. No shroud.

I have used this set-up in the NW of Namibia in the desert, ambiant temperatures of over 40 Deg C using low range for most of the day without any problems.

When like me you have been in a Land Rover workshop and seen the broken viscous fans, you might think like me, electric.

Viscous fans can do two other thing. Fly off and go through the radiator, they don't half make a mess. A viscous can fail and stop sucking the air, in fact running at such a speed that when tested it seems fine but it is actually stopping the air being pulled through the radiator.

Have you had the radiator off and checked, especially a 300Tdi one ? They are very, very good at silting up across the bottom stopping the coolant circulating.

Should you fit electric. Try to remember to switch it on occasionally.

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Electric fans seize up, the contacts corrode and also have fan blades that can damage your radiator.

I've seen a viscous fan cool a chipped TD5 110 dune bashing and towing a disco 3 in loose sand at 45ºc in the desert.

I've also seen electric fans fail to cool an auto box oil cooler and fail to adequately cool a v8 on mountain road climbs in temperate climates.

I've personally had electric fans fail on 2 occasions when I really needed them off road.

3 years and 20k miles ago when I rebuilt the 90 I took the viscous camps advice and refitted one. Bloody good decision I think, 3 mountain trips later and I've never even hit halfway on the temp gauge.

I've thus come to the conclusion that if Land Rover had thought an electric fan would have done a better job they would have fitted one.

Just stirring the worm can :)


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Viscous over cool the engine when it's not needed (high revs high speed motorway etc) and don't cool the engine when it is (stationary on tickover), most of the time anyway. When they go, they go spectacularly and usually take everything around them with them. Yes they are more powerful and move more air but that is at the cost of mpg and power, and slower getting the engine/heater to temp.

Electric fans hardly ever fail in my experience (good ones anyway) they work only when required and improve power and mpg. My TD5 went from 28mpg to 32mpg just by removing the viscous fan. It was noticably more responsive too. I cannot comment on the mpg change on my current 200tdi because the first thing I did when back on the road was throw the viscous fan away. It again though, was noticably more responsive without the viscous fan. When electric fans do fail, they just stop working. No damage to anything. I don't see how the fins can damage the radiator unless they are mounted incorrectly. Mine are wired up with a permenent on option to test if they are working which I test if I am going to be working the engine hard or it is a particularly hot day.

I've run a landy of some form or another with electric fans for 10 years. In the UK they never come on, even off roading and towing (admittedly my off roading is only muddy fields and the odd salisbury plain outing). I dare say you could, as some people have suggested, get away with not having a fan at all in the UK but I'm not willing to risk that.

These threads are always interesting. Where's that popcorn :ph34r:

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Just to add a bit more to the mix... I used to do warranty work for an engine reconditioner who supplied lots of engines for all sorts of applications.I had to remove the failed recon unit and refit a fresh one - then find out why the original failed.Over 90% of the time it was because the electric fan failed,for whatever reason .

Looking at the standard of wiring that most people think is good enough for their home mods I also think this is a good reason not to fit electric.If you are daft enough to dip your vehicle in deep water or sloppy mud then nothing is going to work for long without alot of care.Blocked rads are more common than failed viscous units in my workshop.Cheap aftermarket rads used to be a big problem in diesel P38's too,thankfully they are less common now.

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Ducking popcorn being launched from the seats nearer the back .......... I fitted an electric doins in favour over the vicious fitted to the 200 Tdi in my old 90 and the buggers never come on , I fall into the heating up quickly camp , diesel an all that ,

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My viscous cooled 300 tdi warms up in half the time of my electric cooled 200. The electric fan was incorrectly assembled and boxed, so it was labelled as a puller when in fact it was a pusher, leading to an overheat the first time wit was needed. It was rectified and worse adequately, but is asthmatic compared tot he viscous unit. The stats regarding fuel consumption and power sapping of the viscous fans are utter lies - they are far more efficient than electric fans can ever hope to be.

Do yourself a favour and never fit an electric fan where an engine driven fan can be used. Manufacturers only install electric fans on transverse engines because they know they're excrement.

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