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MG MGA - viscous coupled fan

i have read lots of threads about cooling problems and curing overheating but i have never heard anyone recommend fitting a viscous coupled fan which were standard fitting on many cars before electric fans became popular.
it would seem to me to be an ideal fan for an mga which only needs forced air cooling when stationary. a viscous coupled fan works normally at low revs (tickover) and gives much a reduced fan effect at higher revs when the car is moving.
in theory it should slightly increase available bhp and slightly decrease fuel consumption.
has anyone ever tried one?
my mga has a fast road tuned 1950cc mgb engine fitted with a standard cooling set up and never really gets above 175 to 180 degrees but i would quite like to experiment with a viscous coupled fan if anyone has any info


c firth

It is far easier to simply fit an electric fan isn't it. Gives more of the same benefits as the viscous.
Bob (Robert) Midget Turbo

most owners i have spoken to who have fitted electric fans seem to advise keeping the standard one in place also to keep the car cool. my car seems to run cool enough without an electric one so far (havent run it in really hot weather yet though).
a viscous fan could also be a little quieter i suppose which could be a slight disadvantage as the the general mechanical noise on my car tends to cover pretty much all other unwanted noises (radio, wifes conversation etc etc)
c firth

Viscous fans were a "feature" of the rubber bumper midgets. Once one of them has come apart at speed, they longer seem quite so attractive. Since you have no cooling issues, I would not bother it (if it ain't broke, fix it till it is?), but I would go the electric route if I did.

Dunno why someone would install electric and leave the mechanical in place, however. The fan is most needed when running for significant amounts of time at low rpm, and that is exactly the conditions under which the mechanical fan is most useless. At speed, there is no need for any fan unless it is very hot out and/or you have mixture issues, timing issues, or other problems you are trying to mask by enhancing the cooling, but that is the time at which the mechanical fan is sapping the most performance from your engine. OTOH, an electric fan does not run unless needed and is just as efficient at idle as at 5000 rpm.

The electric fan works best as a "puller" behind the radiator. Not sure how much room there is for one there in an MGA. Rather tight in a 72 Midget, even with the radiator shroud from a 1500.
David "Midget meddler" Lieb
David Lieb

The TR7 used the same viscous fan as the Midget and it was one of the most problematic features of the car when they were just out of warranty. I replace many of them at a couple of hundred dollars a pop. My TR7 daily driver had one when I bought it but it failed shortly after. It was considerably cheaper to fit an electric fan that to replace the viscous, and the electric has done the job very well with no problems. The right fan with a thermostatic switch should have no problems keeping your A cool.
I vote for electric!

Rich
Rich McKIe

They where a popular feature on tractors at one time with a thermostatically controlled flow valve. Sounded good and usually worked for a while but over time they became less effective and would just freewheel around being then no good at all. I would leave well alone.
Most car makers today are 100% electrical in their cooling but they are now working on ways to utilise the heat energy wasted through cooling and retreive the energy. Same goes for the exhaust heat. Now that would be a great modification for classic cars. The more they overeat the more energy we get back!!

Neil
Neil Purves

thanks everybody for all your comments, i hadnt realised that viscous coupled fans were so problematical.
looks like i will be leaving everything unchanged for now. i may go the electric fan route once i have run the car in some really hot weather, will keep you all posted
thanks again
colyn
c firth

Ok ..... so hopefully I'm asking a question that many who read this thread are dying to ask but are afraid of looking stupid ...... I already am ..... so no fear here !!! What the h**l is a viscous coupled fan and how does it work ??
Michael Hosier

Here is a picture of a fan clutch for a Toyota truck.
They slip when not needed and hook up when needed. The bi metal spring in the center senses temperature.


R J Brown

Many thanks RJ. Never knew such a thing existed. Re-reading all the comments again and looking at the sample you pictured, I can see how the whole thing may well be the subject of controversy. It would seem that someone tried to build a better mouse trap !!
Michael Hosier

Viscous is a new word for me. I believe in the States we call that a "clutch fan".

There are units that last quite a long time BUT the MGA has no room unless you remote mount it. Now that would be quite a bit of engineering- a waste of time. Best to stick with the plastic MGB fan blades to drop weight and flow decently and then add a couple of electric fans to the front side. I just posted elsewhere about this but for the sake of the archives..

http://picasaweb.google.com/bmcautos/DennisOberlohS1958MGATwoPlusTwo#5213505615616606994

-BMC.
BMC Brian McCullough

This thread was discussed between 13/12/2008 and 18/12/2008

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