Coming out of Laughlin, NV toward US95, real steep grade for about 15 miles, basicly sea level 6500 ft. Pulling 6000 pds of car on trailer. Truck went to 240 and the wastegate kept opening and reducing my power. Slowed down to a crawl and temp went down. Got to the top to cool down but the engine didn't appear hot. I may have a bad clutch fan.

 

Filling out you're signature would be very helpfull in finding your problems. With a little information on the truck we can start to diagnose the problem at hand.

Not trying to sound mean or anything just need to know the truck.

 

Or a dirty radiator?

 

If it's an old blow-by-bottle- missing -up front set up like mine is, I vote with the Dirty Radiator post - mine was doing the same thing until I yanked the rad and cleaned it REAL good, no problems since....that was at 108K miles

 

I live and work just south of there. I pull that grade everytime I go racing in Vegas. It's a real fun pull when the ambient temp is 120+ in the summer. There are actually burn spots along the side of the road where trucks didn't quite make it up.

98 to 02.... Engine oil leak could be restricting air flow throught the radiator as the others mentioned. 2000 to 2002 had it even worse with the "puke" bottle mounted on the front of the engine. If you are a "high miler" your t-stat might be due for a change. If you coast down a long grade and note your engine temp dang near hits cool, it's time for a new one.

03 up.....I would be checking the fan clutch and see if it's working correctly. They are operated by the ECM and I have replaced a couple that had speed sensor errors, or the harness had an up close meeting with the fan (fan wins every time).