Thermatic Fan on Prado TD

Submitted: Tuesday, Jan 31, 2006 at 11:12
ThreadID: 30287 Views:6965 Replies:15 FollowUps:5
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Looking at replacing the Clutch Fan on the 95 series TD with a Davies Craig thermatic fan. Not having any cooling problems but trying to minimise the adverse power drain when the clutch fan kicks in when towing.

Has anyone else done this and what were the results?

Gold Coast
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Reply By: Member - Roachie (SA) - Tuesday, Jan 31, 2006 at 11:58

Tuesday, Jan 31, 2006 at 11:58
Haven't done it yet, but have been thinking of replacing mine with a set-up off a AU Falcon. This has dual fans and shroud etc. You can get off ebay for about $160-.
I haven't bitten the bullet yet though.
Some of the blokes on here say that leccy fans don't push as much air as a clutch fan, but I'd reckon that twin fans would have to do a better job, especially in MY case as I have removed the original shroud (cos it wouldn't fit once I'd installed the bigger radiator).
The other issue that could be a problem relates to the leccy units not liking to be dunked in water. If I do go ahead, I'd be fitting the fans with separate switch so I can choose when to turn them on. That way, if I'm gunna go through any water, I'd simply turn the fans off. They'd get wet but would dry out and be okay afterwards. I am fairly confident about that cos I currently have a Davies Craig 10" "helper" fan in front of the radiator/air con to assist in the cooling process.....and that's been dunked a few times and still works ok.
Hope this helps a bit. Some people reckon the installation of twin thermo fans cures any overheating problems they've had.
AnswerID: 152035

Reply By: Gerhardp1 - Tuesday, Jan 31, 2006 at 12:13

Tuesday, Jan 31, 2006 at 12:13
A friend has a 60 series with a 350 chev which had twin davies craig thermo fans when he got it.

The fans had no hope of keeping it cool and it boiled when off road at the drop of a hat.

We went to Mark's 4wd and got the adapter to fit a standard Toyota fan onto the Chev, and cut and shut a 60 series diesel shroud so the fan was properly centred, etc.

That was the end of overheating problems. Not to mention the whole thing was much quieter without the electric fans shrieking their heads off.

On inspection, the plastic shrouds, fittings and the fan motot units blocked about 50% of the air flow through themselves, thereby effectively reducing the radiator size as well.

My suggestion is leave your setup intact because it works. The Chev survived the boiling without engine damage but will yours? What would it cost you to repair the damage caused by boiling it?
AnswerID: 152041

Reply By: Member - Collyn R (WA) - Tuesday, Jan 31, 2006 at 12:40

Tuesday, Jan 31, 2006 at 12:40
To effect the cooling needed one has to have to shift a certain mass of air. If the same amount or air is shifted then the energy needed to drive that fan is the same.

However an electric motor is more efficient than belt drive (which may absorb 1 kW)- and is likely to cut in more accurately, so some energy is saved.

This can be appreciable on light loads on really hot days. There, only 15-20 kW may be needed to maintain constant speed on the level - so the fan belt drive may be responsible for over 5% of the total energy required.
Collyn Rivers
AnswerID: 152046

Reply By: prado4x4 - Tuesday, Jan 31, 2006 at 12:50

Tuesday, Jan 31, 2006 at 12:50
Can't say specifically with the prado, but guys with the same 1KZ-TE motor in the surf's have tried using electric fans rather than the clutch fans. Never worked well enough and kept overheating. They went back to the clutch fan.

AnswerID: 152050

Reply By: Wizard1 - Tuesday, Jan 31, 2006 at 14:07

Tuesday, Jan 31, 2006 at 14:07
Thanks for the feedback sounds as though the project is bound to fails with dyer financial consequences. Guess I'll stick to the theory of unless its broke don't fix it.

AnswerID: 152066

Reply By: Raymond from Wanderin 4 Wheelers - Tuesday, Jan 31, 2006 at 14:13

Tuesday, Jan 31, 2006 at 14:13
Hi Wizard

Tried running twin electric fans on a Ford Bronco. Worked fine till we needed low range and then the fans could not push enough air, went back to the old fan belt driven one. One I saw in the US which ran a hydraulic fan of the power steering, worked a treat
AnswerID: 152068

Reply By: Member - MrBitchi (QLD) - Tuesday, Jan 31, 2006 at 14:51

Tuesday, Jan 31, 2006 at 14:51
"trying to minimise the adverse power drain when the clutch fan kicks in when towing"

I'd be amazed if you could feel a power drain when an electric fan kicked in....
More likely your air conditioner compressor is causing it. Electric fans are designed to REDUCE the power drain from the engine, not increase it....
AnswerID: 152072

Follow Up By: Wizard1 - Tuesday, Jan 31, 2006 at 15:39

Tuesday, Jan 31, 2006 at 15:39
I'm talking about a clutch fan, not an electric fan. I assume you know the difference. I want to replace the clutch fan with an electric fan....I'm sure that's what I said?

The clutch fan is operated by the fan belt and when the engine heats up the fluid in the centre clutch causes the fan to engage and turn at higher speed which inturn causes the engine to work harder.

It may not be technically correct but thats the way I see it.
FollowupID: 405649

Follow Up By: Member - MrBitchi (QLD) - Tuesday, Jan 31, 2006 at 16:03

Tuesday, Jan 31, 2006 at 16:03
Reminder to self:- READ THE POST (beats self on head...) Scheech..that's twice in one day for me :-(
Better leave this forum alone for a while and do some real work....:-~
FollowupID: 405651

Follow Up By: Shane (QLD) - Wednesday, Feb 01, 2006 at 09:58

Wednesday, Feb 01, 2006 at 09:58
I'm sure the correct name is " Viscous Fan "
FollowupID: 405892

Reply By: Philip A - Tuesday, Jan 31, 2006 at 16:06

Tuesday, Jan 31, 2006 at 16:06
Don't know about Prados but a Range Rover Clutch fan is supposed to draw 7Kw.
Now 7KW is 7000 watts at 14 volts is 500 amps.
No matter what the difference in efficiency about 25 amps of electric fan is not going to shift the same air as 7KW of clutch fan, or even 1KW. If you reckon that you can feel it , then it must be more than 1KW as thats only about 1% even of a diesel.
Also put your bl00dy shroud back on. Without a shroud you lose a big percentage of fan efficiency.
You have probably done the exact opposite of what is required to keep your engine cool, and the clutch will cut in much more with no shroud because the engine is hotter.. A bigger radiator makes little difference at low speed as the fan creates the airflow across it.
Geez even NEW Land cruisers and Patrols run clutch fans as well as the new Disco. Do you think they do it for fun when the NVH etc is so much worse than electrics, and probably the economy is worse.
regards Philip A
AnswerID: 152078

Reply By: bombsquad - Tuesday, Jan 31, 2006 at 16:43

Tuesday, Jan 31, 2006 at 16:43
I don't quite understand all of the different power conversions, but having had a few bad results with poorly set up electric fans, I went back to the belt driven fan on my mq and fitted the twin davies craig units on the front of the AC unit and put in a manual switch, for sumplimenting the belt driven unit at low speeds.

If a certain volume of air is required to be drawn through the radiator, one would think the same or similar amount of energy is required to spin the blades of a fan to do this. Electric energy isn't free. While (an electric) fan wont be drawing the energy directly from the engine, the alternator has to provide it.

I don't really know, but are we comparing energy efficiency:- of converting torque into electricity into torque (the electric option)

-or torque from the shaft on the waterpump (or similar) into...torque directly to the fan blade. Both the alternator and the origional fan are both belt driven, so they should more or less cancel each other out.

My conclusion (havent the equipment to test properly) would be the only extra loss could be the heat sensitive clutch in the belt driven fan hub being less efficient than the conversion of the torque to elec. back to torque.

I don't think you can beat the origional set up, except maybe with a better, more efficient fan blade.

Anyone more 'educated' have any thaughts on this?

Cheers Andrew
AnswerID: 152084

Reply By: Outnabout David (SA) - Tuesday, Jan 31, 2006 at 22:03

Tuesday, Jan 31, 2006 at 22:03
Just fit a chip. That will give you a far bigger increase in power and torque.
AnswerID: 152163

Follow Up By: Wizard1 - Friday, Feb 03, 2006 at 15:22

Friday, Feb 03, 2006 at 15:22
I already have a Dtronic. But when driving in high heat (35 - 40C) and wind, towing a 1800 kg caravan it doesn't make a whole lot of difference.

Thanks for the tip anyway..
FollowupID: 406488

Reply By: Flash - Tuesday, Jan 31, 2006 at 22:17

Tuesday, Jan 31, 2006 at 22:17
The one thing we all need is an electromagnetic clutch fan, like some older Peugeots had. (maybe still do???)
Perfect, just like an aircon clutch- free wheels when not needed and then 100% direct drive when it all gets a bit too warm.
I had a hell of a battle trying to get my Viscous silicon clutch fan to work when it should- now though, it sometimes works TOO much which wastes heaps of power.

But sadly, nobody makes an add-on electromagnetic clutch as far as I'm aware.
AnswerID: 152165

Reply By: awill4x4 - Tuesday, Jan 31, 2006 at 23:09

Tuesday, Jan 31, 2006 at 23:09
Having fitted thermo fans to a few of the custom radiators I have built, they do work and work well if a properly designed shroud is used at the same time.
A couple of examples: A 378 cubic inch (500-550 bhp) Cleveland in an XW Fairmont running 10 second 1/4 mile times with a custom radiator and AU twin thermo's. Prior to the build up it would overheat between runs at Calder now it will sit in the queue at a Macca's drivethrough and the fans will pull the heat out very efficiently.
A 502 cube supercharged Big block Chev running on straight LPG in a "34" Ford street rod using a 16" Davies Craig thermo will do the same.
The same 16" setup on a "32" Ford high boy street rod and I will use the same setup on the next project, a 572 cube Chev in a "32" Ford "all steel "Dearborn"American body street rod. Out of the crate they're rated at 620 bhp but the same street rodder wants to supercharge it as well. The setups work, you just have to match your components.
I've got a set of Ford AU Falcon fans I want to put on my petrol efi GQ but with my custom radiator being thicker space is at a premium and I think it will foul on the waterpump/alternator belts. If I can find a way of fitting them I will because the Ford electric fans are really "weapon of choice" in all high horsepower/ extreme cooling situations.
Regards Andrew.
AnswerID: 152186

Follow Up By: Member - Roachie (SA) - Tuesday, Jan 31, 2006 at 23:15

Tuesday, Jan 31, 2006 at 23:15
G'day Andrew,
That's a great report and one which gets me back to thinking this may be my best option too. I'll just have to check the clearance between the thicker PWR radiator and the water pump pulley (after removal of the fan and clutch assebly of course).
Have you had any experience with leccy fans suffering after being dunked in a water crossing etc?
Cheers mate
FollowupID: 405814

Reply By: Philip A - Wednesday, Feb 01, 2006 at 08:54

Wednesday, Feb 01, 2006 at 08:54
Idling at Maccas is different to climbing a sand hill in 40C or towing up a big hill..

Pacet in UK sell special waterproof fans at a premium price. That should answer about dunking.
What about your alternator size? Falcons and Holdens have big alternators which are sized to support the draw of the fans under extended idle. if you already have say 120 amps, you would have to consider adding maybe 30 amps , as alternators are not putting out anywhere near max at idle.
It begins to be a very expensive proposition,if you want seamless performance in all conditions..
I have from time to time considered replacing the viscous on my Rangie but have always gone the conservative route. Its no good finding that they are inadequate half way up a sand hill , or a mountain range in the middle of nowhere.

My understanding is that Prado diesels have marginal cooling at best and the intro was delayed for years until they sorted it. I know you have a bigger radiator , but consider the consquences if the thing unavoidably overheats.
Regards Philip A
AnswerID: 152227

Reply By: Shane (QLD) - Wednesday, Feb 01, 2006 at 10:15

Wednesday, Feb 01, 2006 at 10:15
It seems to me that the Terracan Diesel has the cooling aspect sorted out. One big viscous fan followed up with two electric fans in front of the Radiator. I have never heard the viscous cut in ( except when first started ) on the hottest day & the electric fans only cut in when the aircon is on. The temp gauge never moves no matter how hard you push it. Wish the Cruiser was the same as the fan is always cutting in & out.
AnswerID: 152237

Reply By: Outnabout David (SA) - Friday, Feb 03, 2006 at 19:16

Friday, Feb 03, 2006 at 19:16

Under those conditions ie 1800kg and stinking hot day the only way you are going to get extra HP is to buy a Landcruiser as you will not notice a difference in power. If you have a bull bar, take it off, if you have a set of driving lights, if you have bigger tyres thgen take them off and you will get 10 % more power.Putting 70series tyres on will drag out an enomormous amount of power especially if you have an auto. I have previously had approx 10 prados over 10 years both petrol and diesel with and without Dtronic and can assure you from dyno results of the power change with different accessories.
AnswerID: 152803

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