'98 XJ ocassional overheat

98 xj w/ 4.0 was overheating while driving at both highway speeds & city driving speeds, but not at idle. Replaced thermostat & flushed system myself but that didn't do anything. Took to a shop & they said there was a clog somewhere which was not letting coolant flow while at higher speeds. I replaced water pump, radiator & all hoses. That seemed to do the trick until about a month later I was towing a small pop-up camper & it did it again. Ever since then it overheats driving down the highway. Not as often as before. The temp. gauge normally runs at about 200, then while driving it will shoot up to the line before overheat. I will slow down to about 30mph & after a couple minutes the temp will go back down. Anyone know anything I could look for?

Have you checked the fans? My 97 runs at about 210 with the original thermostat.

I would check the clutch fan and the electric fan with the AC on first.

Yes I did. Both seem to be working fine.

alright then...was that radiator new?
I have also heard of a Jeep H2O pump with the impeller turning the opposite direction (it looks the same on the outside) so make sure you bought the correct one.

Another thing, I noticed, I use a Fram PH977A 2 quart oil filter and 5w-50 oil and it brought down the engine temperature slightly as well as increasing oil pressure 10 psi. You can also use a Motorcraft FL-299 or WIX 51773. Engine oil capacity is now 7.5 quarts instead of 6.0 quarts.