Dennis -

Thanks for the suggestions, I suppose I could go back to stock fan, but since the problem only seems to occur at high speeds, the fan shouldn't even be needed. Any faster than 45 mph I would think the fan should make no difference, and this problem only has happened on the highway or freeway.

About the engine clog suggestion: Are you saying a radiator shop can check my engine for proper flow? Or just the radiator? I have not done anything to check if my engine itself has a flow restriction so I guess that's a possibility. Also what is a power flush and is it different or better than a regular radiator flush you buy at the store and run in your radiator for a few days?

By the way I replaced the radiator so it's not clogged. The water pump is new as well. Almost everything is new except the engine lol... I'm interested in this clogged block idea though. Isn't there any way I could test for that myself?

I know it is flowing, when I fill the radiator up so it is nearly full, if I remove the radiator cap and let the engine warm up to operating temperature so the thermostat is open, I can see water flowing past and if I rev the engine a bit the water flows faster. I don't know if it's ENOUGH flow though.

Also, I tested the radiator for exhaust gasses (blown head gasket) and the test showed no gasses so I don't think the head gasket is blown. Also am not losing any coolant or gaining any for that matter. One thing I did notice however is that if I let the engine get nice and hot, like over 200 degrees, and I watch the radiator with the cap off, revving the engine a little bit will produce bubbles. This is after it has been thoroughly "burped". I assumed these bubbles are steam due to boiling water in hotspots, because the cap is off so there's no pressure thus the water boils easier. Or would these bubbles be something worse? They didn't show up as being exhaust gas so I figured they must be water vapor from boiling.