I picked up this 95 XJ in January and I've been daily driving about 50 miles round trip to work and back trying to see if any issues pop up. In the mornings it's pretty wide open and I can do about 65mph the entire way. On the way home, it's usually stop and go for a couple of hours. It usually runs about 190-210. It's been pretty cold (for So Cal standards) the last couple of days and temps won't seem to get any higher than this. This pic was taken after 20 miles of 65mph with an outside ambient temp of 45ish degrees. Running too cold? Is the thermostat stuck open? How do I check that? Or would you consider this normal operating temp for the conditions and I will be happy when July comes around?

 

The only way you'll know is if you take the t-stat out when the coolant is cold. if its open then theres the answer. You can also check to see if the t-stat is opening too soon by putting it in a pot of water and then bring it to a boil. Use a thermometer to test water temp and when you see the t-stat start to open ( t-stats open pretty slow once they reach temp, so you have to really watch it to see when its opening) check the temp and see if its opening within a couple degrees of the t-stats advertised temp. It should probably be stamp on there somewhere...

 

Looks about the same as where my gauge sits during the cold months.

 

That's where mine was sitting. I suspect the PO removed the Tstat in mine. So far I haven't gotten around to checking because it developed rod knock a few days after I got it. But I did drive it enough to find that the mpg was quite low and I expect it was having a hard time reaching closed loop operation with it staying that cold. Is you mpg like 8-10 or more like 15?

 

One clue towards thermostat stuck open is slow warm up to operating temperature.
You might not have had your xj long enough to be able to tell, though.

 

correct. How fast does it warm up to that temp?

 

They are designed to open when they fail, so I would not be surprised if that's your issue. If you just bought it you should be going through the fluids anyway, and I'd rank coolant right behind oil. Replace the thermostat while you're flushing it and make sure to go with an OEM Mopar. Some also like the Super Stant.

 

Since the weather in NJ has taken a turn for the colder, that's roughly where mine sits if I'm not in stop-start traffic. When it warms up again I'm sure I'll be pushing 210 again. Either we have the same exact issue, or this isn't really an issue at all.

 

I have not calculated MPG yet. I will the next fill up to see where I’m at. I’m not sure what kind of mpg I should be getting. 4.5 inch lift on 32s.

Let it idle to warm up and see how fast. Or drive normal and see how fast? I’ll time it out tomorrow on my way to work.

 

drive it.

 

Took about 4 and a 1/2 minutes at 50 degrees ambient temp. All surface streets then about a half mile of freeway before coming to temp. Stuck around 155-160 the 24 miles to work.

 

Get a factory stat.