When you say you "switched to an electric fan", do you mean you no longer have the stock fan/clutch setup? Or did you switch your electric fan only.

 

It's probably your radiator being plugged. I've also seen where the lower radiator hose on some vehicles gets old and loses it's stiffness. At high speeds it can collapse (sides such in). Then it restricts water flow to the motor and it overheats. It's hard to see because it happens at high speeds. You can simulate it by revving the engine at higher RPMs and seeing what the hose does. I've also seen the impeller on the water pump (which is pressed on) gets loose and slips at high speeds, when the engine is warm, yet has enough friction to pump at idle. This isn't common at all, but it happened to my brother once. It was a bugger to figure out. So, water pump might be something to look at. Of course quadruple check that the thermostat is good and isn't in backwards and the fan is the right direction and belt is properly tensioned.

Generally speaking, the standard engine fan will probably pull a lot more air than an aftermarket electric fan because the factory shroud pulls air through the entire surface area of the radiator, rather than right where the electric fans are. But if the problem happens at high speeds, it's not fan related.

 

Had this on my D1 a couple of months ago, it's the radiator. Pull it out and take it to a shop to have it rodded/cleaned. Cost me $50.00 and no problems now. Also when you disconnect the Trans Cooler and Oil Cooler lines there are small black o-rings. Make sure to pull them off and replace them with new ones, causes leaks. At that mileage and unknown history, replace water pump, hoses. Might as well do the belt to since you have to take it off.

 

The problem with the DI radiator is that when the DI came out new there was no such thing as "aluminum safe" coolant, so they used the standard green stuff and said to change it every 30,000 miles or 24? months.
How many people do you think actually did this? Who thinks about engine coolant until there is a problem?
Standard green coolant will corrode and clog a aluminum radiator if it is not properly maintained.
Because it had green coolant in it any mechanic working on it will not think about switching to a aluminum safe coolant.
So get a new radiator, switch to Peak Global Lifetime coolant and then change it every 2 years and you should never have cooling problems related to the radiator ever again.

 

By "switched to electric fan" I meant that the factory fan and clutch assembly was removed completely and an electric fan and shroud was put in its place. I took the advice on the radiator and switched it out with my '97 which didn't give me problems. So far this has seem to help it. I should know more tomorrow when I'm able to test it more.

 

Hey guys,

Just wanted to update on my situation. After switching my radiators I really put it to the test today. The temperature outside was over 100 degrees and I towed a Durango on a trailer on a 2 hr trip. On the way back I towed a BMW 3 series on the same 2 hr trip. My temp gauge never budged. I feel safe in saying that if it made it today then its good to go. Turns out you guys were right once again. Thanks for everyone's help.

 

Glad to hear!