[Angus Martin]

Alright guys, what the best blow through thermo to run?
Plan is to mount one on the front of the radiator to blow through it when 4wding.
What's a good brand or other info I need to know?
Cheers

[watermouse]

The short answer is the largest diameter one you can find. But even that is a terrible idea.

The problem with front mounted fans is they only flow air through the section of radiator directly behind it.

The best fan for 4wding is a belt driven viscous fan with a shroud. The most reliable and efficient way of drawing air through your radiator when driving speeds are low and engine load is high

[Angus Martin]

Sorry, I should mention I've already got a Vitara viscous hub fan on it, and I'm about to put a shroud on it but thinking of putting this on as well

[Gwagensteve]

Don't do it. The Vitara viscous fan, sierra radiator and shroud will cool the car just fine. When the pusher isn't running, it's shrouding the radiator in front of the viscous fan, making the heat acrivated clutch see the wrong temperature.

[Angus Martin]

Hmm ok. It's just gonna be subjected to very high temperature and load. I'll take your word for it though, thanks
And also, you speak of this vitara viscous fan as being heat activated but mine seems to alway be on, even on a cold start (I obviously can't check when the vehicle is a high speed)...

[fordem]

The viscous fan is always on, just not always at full rpm - on a cold start, it WILL be on, the viscous fluid that drives it will have settled to the bottom of the clutch - here's a quick way to test.

1) Before starting from cold, open the bonnet and try to turn the fan by hand, it should turn, but with a fair bit of resistance.
2) Start the engine and let it idle for about 1~2 minutes, and then switch off - what you're doing is allowing the centrifugal force of the spinning fan to redistribute the fluid, but not allowing the engine to warm up.
3) Immediately after stopping the engine, try to turn the fan by hand again, it should turn, this time with less resistance than the first time.
4) Drive as per normal, when you get to your destination, by which time the engine will have reached operating temperature, switch off and immediately try to turn the fan by hand - depending on how hot it was gotten, the fan resistance should be more than in step 3 but less than in step 1.

You can also listen to the fan - open the bonnet and start from cold, you should hear the fan quite loudly at engine start and then the noise will rapidly diminish as the fan speed drops off.

[Gwagensteve]

As per fordem. It's always turning, although until the engine is hot, it's not locked.
When you start the car from cold you'll hear a noticeable roar, which is the fan locked as fordem describes. Once in motion you'll rarely hear it. Notice how the hub is alloy and finned- the temperature of the air flowing over this is critical for correct function. Shielding it by having a pusher fan hub in front of it will impede its operation.

[Angus Martin]

Cool, good info thanks guys, you learn everyday

[Angus Martin]

Worth swapping an aluminium radiator out for a copper one or is the difference in specific heat capacity/thermal conductivity negligible?

[Gwagensteve]

I can't see the need for alloy.

If you currently have an aluminium tanked radiator I'd leave it alone. If you have a coil (or late leaf) Sierra plastic tanked alloy finned radiator I'd replace it with an all alloy or all copper radiator. My preference is all copper for ease of repair.

[Angus Martin]

I've got a new all aluminium radiator in it, car came with it

[losfer]

Angus , people gave you good advice in the other thread . forget the thermo fan they usually cause more dramas than they are worth.

As long as your cooling system is up to scratch as other people have mentioned , you wont have a problem.

i'll point out a main failure of overheating. Most people when prepping for a trip like yours, replace their radiator hoses . Most people dont replace ALL their water hoses and its usually the old hose they dont replace that lets them down. So replace any hose that carries water.

Replace your thermostat if it hasnt been done or is of unknown history.

[Angus Martin]

Thanks, I'll go over it all and forget about a thermo.

[Gwagensteve]

Good point losfer. Heater hoses fail at least as often as radiator hoses.