Fan Thermostat

[Paul Blore]

Hi,

The fan on my Cobra is switched via toggle switch on the dashboard, which is generally okay, although I have on a couple of occasions forgotten to switch it on when required, which has resulted in the water temperature getting a bit hotter than it should. I'd like to fit a thermostat control, what is the best way to achieve this? I've seen the dial thermostats that have a probe, which is connected to the top hose, are these okay?

Thanks,
Paul

[Roger King]

Not really. They're not very nice to look at and the Kenlowe type require a probe shoved either in the side of the hose, or between the rad fins. Both are very bodge-like in my opinion. And you're right, I'd never trust myself to switch the fan manually. You only need to miss it once...
Do you have single or twin fans?
My 289 had/has a single, so for this:
A threaded boss (readily available from Demon Tweeks, Revotec and myriad others, you can get brass or aluminium) welded or brazed into the top tank of the radiator to take a thermostatic switch. This is wired direct from an ignition-fed circuit via a relay. The fan comes on automatically, no need to override.
I can't remember the thread size offhand, but you can go aftermarket or use a stock modern manufacturer's switch. There is a massive choice of temperature ranges to choose from. I use something like this:
http://www.ebay.co.uk/itm/RADIATOR-FAN- ... 35c9ac3aab
Here are some numbers for temp range ref, enter the number in ebay etc. and they'll usually come up:
http://www.x-eng.co.uk/X-ThermData.asp

My Mustang has twin fans, which are set on a twin switch from, I think, an Alfa. This looks just like the one in the first link above, but has three connections. This way one fan is set to come on at a lower temp, and if that's not enough the second fan will come on at a higher range. Again, no overrides, I prefer it all to be automatic. And if it fails it's not likely to be the switch so won't make any difference. You'll need two relays, obviously, for this setup.
I don't like adjustable fan controls - I've had several, from the 1950s radio-dial Kenlowe thing to an all singing, all dancing US programmable controller with presets. You spend your entire time fiddling with the damn thing just in case it's not quite where you want it, or (as with the fancy US one) it's so complex the electronics fail on you. The switches above, which I use, are all manufacturer spec and have to be reliable.
Coupled with Evans coolant and a zero-pressure system, what could possibly go wrong?
Ouch, just bit my tongue. Shouldn't stick it in my cheek like that.
Roger

[Paul Blore]

Thanks Roger for the comprehensive reply as always. I'd have put money on you coming back with the answer.

I agree about the dial thermostats looking ugly and I was hoping that wasn't the preferred solution. I think I have a blanked off threaded hole in the top of my radiator, but I don't know what size it is so I'll have go and check.

I have a single big fan that has always managed to control the temperature, regardless of conditions. I rarely have to turn it on because the radiator is so good, but that just makes it all the more likely that I'll forget.

I've been contemplating the waterless coolant, but it seems to be a bit of a rigmarole to change from normal coolant to waterless.

Thanks again,
Paul

[Roger King]

Thanks Roger for the comprehensive reply as always. I'd have put money on you coming back with the answer.

I agree about the dial thermostats looking ugly and I was hoping that wasn't the preferred solution. I think I have a blanked off threaded hole in the top of my radiator, but I don't know what size it is so I'll have go and check.

I have a single big fan that has always managed to control the temperature, regardless of conditions. I rarely have to turn it on because the radiator is so good, but that just makes it all the more likely that I'll forget.

I've been contemplating the waterless coolant, but it seems to be a bit of a rigmarole to change from normal coolant to waterless.

Thanks again,
Paul

Hope it helps. Changing to Evans is actually no big deal - most of my cars have had it from scratch, so no problem - but I changed my daily BMW 330i over a couple of years back and it wasn't difficult. Empty the rad, hoses and block (need to locate the block drain plugs, unscrew and refit with a bit of PTFE tape), then refill about half the system with neat ethylene glycol antifreeze, the cheap stuff. Run it up till it just gets warm, switch off and drain again. Then refill with neat Evans. That's how the Evans guys told me to do it. I tried to buy their 'prep' fluid, but they wouldn't sell it to me (don't think they had any!), they just told me to do the above!
You'll need a decent recovery tank as it expands a fair bit, but the hardest part is finding a zero pressure rad cap. You can always knock the spring out of a normal one. 25k miles on the Mustang now, and the insides of the cooling system still look like they've been polished!

[Roger King]

This Nutone RFTH95 Wall Switch automatically allows your Roof or Gable Exhaust Fan to come on automatically. Once the Wall Switch is installed, the Wall Switch turns the automatic thermostat turns the unit on and off to exhaust heat buildup.

Hmm... now, where could I install a Wall Switch? Oh, I can think of a place. Bend over, Jules...

[BrianC]

Coming back to original question! Of the vast array of temp ranges available, which would be the best for a 3.9 RV8 powered Hawk fitted with twin fans, and what is the current thinking for engine thermostat?

[Fireball]

Hi Brian,
I have exactly the same dilemma, except mine is for a Ford 260. I've used a 82 degree thermostat and I was going to use a fan switch from carbuildersolutions but not sure of what temperature range to go for. If the stat opens at 82 then maybe a 95/86 switch would be the one to go for:

http://www.carbuildersolutions.com/uk/f ... 6c-m22-x15

I suppose we need to find out what is the design temperature of our engines and go from there?

Good luck

James

[Roger King]

Hi Brian,
I have exactly the same dilemma, except mine is for a Ford 260. I've used a 82 degree thermostat and I was going to use a fan switch from carbuildersolutions but not sure of what temperature range to go for. If the stat opens at 82 then maybe a 95/86 switch would be the one to go for:

http://www.carbuildersolutions.com/uk/f ... 6c-m22-x15

I suppose we need to find out what is the design temperature of our engines and go from there?

Good luck

James

SBFs (well, 260 and 289) had a design temp that required stock installation of a 195° radiator thermostat in Falcons and Mustangs. But we are not running a stock setup - radiator, cooling fan, engine bay, transmission loads, car weight, not to mention state of tune are all very different from any stock Ford application. Ford also used a thermostatically-controlled vacuum take-off to raise engine speed if the car got hot, to increase water pump output.
I'd say your suggested thermoswitch would be a very good starting point. I'm afraid the only way to find out (that I know, anyway) is to try a few different ones and see which you like best. I buy mine from the autofactors on ebay, much cheaper, but you'll need to use the chart above for part number cross-reference.

[nikbj68]

We have a Revotech fan controller on the Greyhound, which works a treat.
http://www.revotec.com/acatalog/EFC_Hose_Fitting.html