well this things only got 34,000 miles.

I was told the water pump was changed, it was bone stock, nice older guy had it and his wife drove it until she passed in November.

I had not messed with the cooling other than checking fluids but last super hot day going up the grades with the air on I was going up to the red and the engine light would come on.

Turned on heater and it dropped back down within 30 seconds.

I didnt push it, just kept the air off. Got back in town and the same thing would happen just on the flats later that day.

Fans all working, Water pump should be good, belts good.

Today I drove up their again, not as hot out and it seemed to run just under or at 220 this time.

Tonight I drained the coolant, used some flush stuff, distilled water flush as well, then added new coolant. Changed thermostat with new 195 stat.

Drove down the street about 10 miles, warm out, got around 210 pretty fast, heard thats normal, but dont want to over heat anymore, hope this fixes it.

Also, when I shut off the jeep, for about 15 seconds I hear the pressure releasing from the rad cap, should I get a new cap also, its only 12 years old lol.

 

What year model is it? I hope it's not a '00 or '01.

But it sounds like it is.

 

Might've just been a sticking thermostat, which you changed. I'd do the cap too.
210 is normal.

 

no sorry forgot to add that, its a 98 4.0

it may be fine now but another thing I notice is the overflow tank never seems to get any action. SHould the cap be hissing?

 

Replace the cap and see if the hissing stops. Is the radiator staying full after it cools?

 

so far, I will check it tomorrow again.

 

Radiator cap seems to be one of the most overlooked cooling system components.

 

that and the fan clutch.

 

Eliminate the guessing game on a 14+ year old car, replace all cooling system components, drain/re-fill coolant once. After all components have been replaced, the guess list becomes very short or non-existent.

 

still overheating, about 90 degrees in town, air on, kept pushin to 220 then just went up and over. Air off fine, 210ish. Freakin had it!

 

Probably should stop asking questions and get your hands dirty. As already mentioned, quit guessing and start putting new cooling system parts on. Upper and lower hoses, t-stat, water pump, fan clutch and if need be, a new radiator. You can do the hoses, stat(which you've done), and water pump for less than $100. I'd say if that doesn't help, pop on a new rad. Fairly inexpensive and one of the most important systems in our jeeps. A good cooling system will get you to 200k plus!

 

Well sounds like it's time to do the maintenance everyone is suggesting.......

Was it supposed to magically cure itself overnight?

 

This caught my attention from the original post "water pump was changed". Also the flushes to the system. I had an overheating issue when I first acquired my XJ a couple years ago. Cause of my prob was isolated to two problems:
1. Bad coolant tank cap was not sealing
2. Air was in system
Replaced cap and burped/purged the air from the system. Now the XJ runs cooler than I would like at 190F. In winter at highway speeds it is much lower than 190F so I have little heat coming from the heater.
Be advised the first cap I bought from NAPA was defective, it didn't seal properly. This caused much confusion diagnosing this problem.
So are you loosing coolant? If your loosing coolant where is it going?
I would get a good light and eyeball for leaks before replacing parts.
I would be curious as to exactly why it's overheating.
That's just me, I guess.

 

Thread's gone full circle.......over heating to under heating......hummmm,..... neither is good.....still guessing.

 

Is your aux fan operating? Should run with the AC on that year, IIRC.