Originally Posted by DrDirt

Ahhh, but if you have an area between your fan blades and the radiator that is pressurized, that means you have all those nice cool air molecules stacking up at the fins waiting their turn to go through. Additional cool air outside the fan will not jump into the fray because it is high pressure there. Why should they go there when it is easier to avoid all that high pressure nonsense and take the easy way and go around? The molecules in the pressureized zone are trying just as hard to go back through the fan blades the way they came in as they are trying to get through the radiator fins...that's why it is called pressure.