LucasYost

I have a 1996 XJ 4.0l.

For the past year or so my jeep has run significantly under normal operating temps in weather under 60 degrees. It runs in the range of 160ish to 180ish but never 200/210 which is normal.

This first was evident with the factory tstat which I then replaced with a Stant 195. This seemed to have made the problem worse. The Jeep would hit 210 and then drop to 160 and not move.

I recently bought an oem Mopar 195 stat and put that in. Now it just gets up to 180ish and then randomly goes between 160 and 180 and never hits 210.

I have not used an IR thermometer because my heat heavily reflects the operating temp of my Jeep...
160 = lukewarm/cool
180 = warmish
210 = HOT

I am extremely puzzled by this situation because to my understanding, the engine temperature is solely controlled by the tstat, which currently has a genuine manufacturer replacement part and is not running like it should.

What things should I consider looking at and troubleshooting/testing. I have flushed the system, burped the system, and replaced the thermostat (and housing)

This issue is driving me nuts. I froze all winter because of this and now that it is warmer I am more than happy to get my hands dirty in this sob.

nujeepguy

if the stat is working it should get up to 210+-
strange, still points at stat??...not backwards? dont really know what that does.

fb97xj1

Point an IR thermometer at the thermostat housing. What does it read when the gauge says 160, 180, and 210?

DFlintstone

Yea, be sure of it's temp. Your heater core may or may not be the problem, also the dash gauge is not reliable.

IIRC it was a stant I had, and a similar issue. I pulled that and got the spendy mopar, ($22?). The Stant had two struts and the mopar has three. I took that Stant and heated it in boiling water. Due to a slight bend of the struts it didn't seat right. Held to the light I could see a crescent of light coming through. I tweaked the the struts to have it seat and put it back in the box for a spare. My heat is still on the cool side for 10 min or so, but my first 10 minutes are straight down, I get heat when I hit the gas.

Thanks to the fog coming in I was able to photo the sun directly. This a bit before total solar eclipse. That's what the light through the Stant looked like, couldn't find the photo.

LucasYost

I will try and get my hands on an IR thermometer