just out of curiosity, what engine temp would you expect to have with a stuck open tstat? i mean how far off am i from a believable number?

you're probably right. i think i will have it serviced at the jeep dealer. its almost due. i will ask them to verify the gauges. although i feel i have already verified the temp gauge with the IR thermometer.

when i said it fluctuated between 180 and 210 it was a range. the factory gauge only has 3 numbers printed on it so it was a estimate. i could have been looking from the wrong angle. i think it would be impossible to read that gauge to an exact degree. all i know is that my tstat was stuck open and after i replaced it my running temp increased 30-40 degrees (another estimate) and my oil pressure decreased 20 psi. both gauges now show "normal" operating temp and pressure. but who knows? my gauges might be completely wacked.

 

Yep. I agree.

 

U've been experiencing low temps for 2 reasons, IMHO.......open stat and wacked gauge. The mark just to the left of middle ( between 1/4 & 1/2) is 182.5. With a new 195 Mopar stat and a accurate displaying gauge, I would think the needle would be very constant just a tick to the left of middle.

 

Just a tick to the left of middle is correct.

 

And the crowd cheers! Good find, well done. , and nice photo, npk.

 

Just replaced my thermostat yesterday too. It was a 195 failsafe, that had failed safely, probably the day after I put it in this past summer. Now that it's getting colder the XJ wouldn't reach temp to get the heater hot, so yesterday I replaced it with a 195 Stant. Heater works great now! I was really afraid it was a heater core clogged beyond repair (I had flushed it several times already.)

XJ gets to temp now in about 5 minutes, and stays pretty stable at 195. Put in a 2 row CSF radiator too.

 

Instead of calling it a "fail safe" stat, it should be called a "fail open due most likely to some other cooling system component failure or operating condition" stat. That's almost as catchy a phrase, no?

 

Might as well call them "opens once"

 

Did u figure out what caused it to "fail safe"? I think the motor gets pretty toasty, to cause it to lock open. Ooops, missed the part about the new rad.

 

This is the first time I've viewed this thread. I just had to; six pages of posts must have meant it was an important thread.

I'll go back to sleep now. Good night.

 

I doubt it'll be put to rest that easy.

 

djb383:

I've noticed on my wife's 88 that the heat output seemed low even with a Mopar stat and the gauge reading 200. My DRB verified that part.
Stuck a temp gauge in the vents this morning and got 130* to 135* outlet temp. I flushed the core last year with whit e vinegar and it got a bit better. Probably gonna do a CLR treatment on the core before it gets real cold here.

 

Check the CLR FAQ 1st.

http://www.jelmar.com/faqclr.htm

 

So, I need to neutralize it with a baking soda and water solution.

 

If that's what it says at the CLR site. If it wasn't in there, it wouldn't have to be neutralized or one wouldn't have to worry if it did get neutralized.