Jeep Cherokee

I have a 1999 Jeep Cherokee Sport w/ a straight 6 4L w. 116000 miles. I was driving in Colorado about 3 weeks ago. The car was packed and the AC was OFF!! Going up hill I could not get over 45 mph. Then on a relativly flat stretch it began to over heat. This happened at about 9000 ft elevation I went up to about 11000 and not for the first time. The car over heated at least 3 times. and the other times were on inclines.

About 4 days later I drove it 200+ miles at 75mph on flat terrain with the AC ON and no problems.

My buddy was driving a 2000 Cherokee Sport with the same load and mileage yet had no problems - He was blowing by me up the hills.

Any ideas why she’s over heating???

You may have a small headgasket leak causing the trouble. Have a block check done to see if that is correct.

Well because you had such a loss of power I tend to think of a blocked or temporarily overheated catalytic converter, which given the age and mileage is possible. If there is an issue with the engine itself it can overheat the converter, or the converter may have been bordeline and the trip stressed it to overheating.