Pusher fan: Top, middle or bottom of radiator?

[xaircav]

Where is it the most effective?

[parkwood]

as close to the top as you can get it.. that's where the hot water comes in..

[Speedbumpauto]

I'd love to hear some fact/engineering based opinion on this because I don't think it really matters. The fan will push X amount of air which will remove X amount of heat. Whether it does it with the hottest coolant or slightly cooler coolant nearer the center, Does it matter? That's the beauty of a shroud, it gets some air to all the fins instead of just a localized area, but it also starts to act as resistance to flow at some cruise speed. Good factory units almost exclusively use puller systems with shrouds so that's what I try to do. I've seen some shrouds with flaps that open at cruise but are sucked closed when the fan comes on. To me, that's the best of both.

[parkwood]

you are right, if you're running a shroud that covers the whole radiator. i see a lot of guys who run steel fans (flex or hard) without a shroud and if they don't get the fan as high as they can the motor will have a hard time cooling. if the hot water comes in at the top and it doesn't get any air pulled thru the radiator until just before it goes back into the block you will over heat... etc: stop lights on a hot day, running around the fair ground at a show,, how many times have you seen cars boil over doing that?
I've had very good luck cooling components, they have the shroud that covers the radiator and the little flaps on the bottom. move a lot of air and it comes thru the whole radiator..