Operating Temp Problem

Well I have been having on and off cooling issues and I want to get this fixed.
My Jeep has a new water pump (last year)
Changed the tstat 3 times (currently have had an OEM one installed for 2 months)
Rad was replaced before I bought it... probably around 3 years old

Now the story...
My Xj never seems to run right at 210F (100C for Canadians), it is always significantly cooler... I cannot figure this out, the temp will rise close to 210F then all the sudden it will drop when driving. If I am sitting at 210F at a stop light and then take off the temp will drop.

Heat works great at 210F, as soon as it drops, no dice
Anyone know what this issue could be?

Next problem is when I am driving around really slow after she has "warmed" up eventually I WILL overheat. Last night I was on a short snow tour with my buddy and my jeep was overheating in -10C weather, the E-fan never kicked in because I didn't managed to get it that hot but it was certainly over 210F and my heater was melting my skin.

So I would argue that the temp sender is pretty much accurate. With my second problem, I am pretty much pointing my finger at my fan clutch, I work at Partsource (sorta like a Vatozone) and we carry the hayden fan clutches... should I stay away? I would convert to electric but I hear too many people eventually switch back to an E-fan because it just doesn't end up pulling enough air. I am not butchering shit to get a taurus fan to fit either.

Under "normal" driving and highway my temp guage is usually in this ball park:


If I am using my heater it stabilizes somewhat... and runs at that temp above, if I don't, it will hit 210 and bounce to that yellow indicated line. I'm stumped on that one, only thing I can think of is the water pump is pulling too much coolant.

How stable my temperature is seems to be in direct proportion to how sealed my cooling system is. It can suck enough air during a cool down cycle to eventually cause problems, even with a tiny leak someplace. With a little air in the system, mine seem to go from too cool, to over heating rather quickly.
Making sure mine was absolutely sealed, a good OEM thermostat with a bleeder hole and a new clutch fan cured my under cooling/ overheating problems.

I should also mention that my wagon is a 1996 just to clarify that I don't have a closed cooling system.

J-Roc said:

I should also mention that my wagon is a 1996 just to clarify that I don't have a closed cooling system.

Click to expand...

The 96 can also have air problems, but they do seem better at moving the air back out of the system. Try squeezing the top radiator hose together with your hands a few times and see what the temperature gage does. Watch the level in your recovery bottle closely, between operating temperature and after a cool down cycle. There is often an inch of difference in the coolant level in the recovery bottle, no or very little movement can be a sign of a tiny leak. Sometimes too much coolant can migrate to the recovery tank.
The heater valve can also cause problems, I noticed when my old one got plugged, the temperature swings in the system became more pronounced.
The last time my 96 was acting up, it turned out to be a pinhole radiator leak, inside upper right hand corner under the fan shroud.

Sounds like the system is not maintaining pressure, got a 16PSI cap on there ? thats what it takes, not a 13lber like the store parts lists show.

I have a factory cap on there... perhaps I should replace it. I didn't even think of that? Maybe that release is buggered

J-Roc said:

I have a factory cap on there... perhaps I should replace it. I didn't even think of that? Maybe that release is buggered

Click to expand...

I do a new OEM cap every two years when I change my coolant and flush the system, I also only use DISTILLED water, that may have something to do with still having my original radiator in my 98 with almost 400,000mi on it. I keep the old one for a spare in case I loose one out on the trail or someone else does which has happened twice and on the same day, darned if I didn't have TWO old ones under the back seat.
I have a brand new Rad in my shed, still in the box, bought it 2 years ago, just in case.