TD42 radiator fan limitations

[MuddyTroll]

Can I use my heat gun to alter/sharpen the angle of the plastic fins on my cooling fan to draw more air through the radiator or will that mess with the fan clutch settings.

I remember reading about thermofans restricting the air flow through the radiator at high speeds (110kmh+) because they simply cannot draw through as much air as is pushed through by the vehicles own speed and so the engine temp rises during sustained high speeds.
So... I noticed the angle of the standard fan is quite shallow and may be causing this to happen to my truck. It has no trouble keeping cool upto 100km/h. I can't even get it above 1/4 no matter how hard I work it, even in +40 degree heat, so the fan has no trouble drawing enough air through the radiator at low speeds. But above around 120km/h the temp rises right up through 3/4 without showing signs of stopping. When I back off to 110km/h, the temp returns to 1/4 in less than 20 secs (no bullsh*t!!!).
Has anybody played around with this sort of thing or used different fans that do the same thing? Will this stuff the fan clutch? Do I need to modify the clutch to make it work and how?

Anybody got an opinion about this?

[Prados]

I wouldn't mess with it. If you put the fan out of ballance you'll eventually have fan blades sticking out of your bonnet.

[chimpboy]

Once you're doing above 25km/h or so, your fan is no longer doing anything to cool your engine. The air is being driven through the radiator by your road speed.

I doubt that they would be all that restrictive. I guess it's possible, but I seriously doubt it is a significant factor. A working TD42 cooling system can easily cope with higher road speeds so I believe you have some other issue.

One thing you could look at though is whether you can direct any more into the radiator, for example with a small spoiler at the front of the car, to catch some of the air that normally just goes underneath.

There is no way you are going to be successful with reshaping the plastic fan though.

[mkpatrol]

Also, for the engine temp to drop in 20 seconds is unusual, it should take a few minutes depending on the cooling system.

Check your guage for accuracy, it may be getting stray voltage from some where causing this issue.

[chimpboy]

Check your guage for accuracy, it may be getting stray voltage from some where causing this issue.

Good point, you would probably want to check actual temp.

Temp going down so fast also makes me think of a coolant issue, eg low coolant, air pocket, cavitating water pump at X rpm, or something. I would replace the thermostat as a basic maintenance measure as well, and make sure you have the right pressure radiator cap on, and that it's in good order.

[MuddyTroll]

Thankyou all for your help.
I have heard that the standard temp guages can be a bit dodgy.
I'll get that sorted first. The last time I serviced the cooling system was over a year ago so would'nt hurt to give it another birthday as well.
I am sure judging by how steady it is working hard at low speeds that the cooling system is working well, but I'll have a look just in case.
It is more just an annoyance really. I just want my pride and joy to be perfect like everyone else.
It's not too often I'll be pushing 120km/h anyway.

Cheers

[love ke70]

havnt got a radiator half full of mud do you?

[MuddyTroll]

Nup. That was the first thingI checked!

[mkpatrol]

havnt got a radiator half full of mud do you?

This was the reason my original radiator was buggered, 15 years of mud caked on the radiator had caused it to corrode from the outside.