Zeig,

Slow down. One thing at a time.

Don't overload the system.

It is far more important to examine the whole cooling system than it is to only worry about a fan. Fans actually do not cool, they only move air. Run a fan inside a completely closed box and the air inside will get warmer.

yes i know, im moving air through the radiator to cool the liquid that goes through it, similar to in a car.

How much heat do you wish to remove?

What is the ambient temperature, the fluid temperature, and the desired output temperature? If you want to get technical about it, (I assume you do since you are asking on an engineering forum) You would need to know at MINIMUM these three things, and Ideally you would want to know specific information about the radiator itself.

If you don't want to get technical about it:

I have used 12VDC high performance motorcycle cooling fans with much success in many applications where size constraints were an issue. I built mobile food delivery vehicles, (both hot and cold food storage) and the motorcycle cooling fans were the perfect candidate for my particular application.

Motorcycle cooling fans

You want them to be ducted, so the air is not simply circulating in circles.

...and how big is the radiator and what liquid will be circulated in it, and then you may want to think about some type of pump to circulate that liquid...as Tim The Tool Man always said..."MORE POWER!

radiator: http://www.jegs.com/i/Flex-a-lite/400/4110/10002/-1

heat removed: anywhere from 400-700W

ambient temperature: will very from 70-90 degrees Fahrenheit

coolant used will probably be that used in computer liquid cooling systems or car radiators.

would some high end computer fans work? i need them to be battery powered

and PS: i love to get technical haha