Getting off subject, but I'll add I use a 2 1/2 gallon garden sprayer with a fine mist through my radiator ( fan is a puller mounted outside) and I can bring mine down 30 to 40*'s really quick between rounds. I don't have to use it often, but it's always in the trailer when I do need it.
We have a few guys that use a pump and pump water out of a cooler through the motors. Cheap cool box, but it works. An old idea that people use to do was a hot bottom end (bottom filled solid) and cold heads.