This is what 195F looks like on the factory gauge. Had to idle for a while to get it up there.

 

318sixpack,

I get the same "low operating temp" thing on my 95. Without OdB2, I can't easily tell whether I'm open/close loop, but I also figured t-stat was wonky.

Cruiser is always adamant on "Mopar t-stat" and I DID in fact swap in a mopar t-stat.... no change....literally no change.

I'll occasionally get "proper" temp on the gauge... ironically cold weather seems to help... but mostly seems to run cold and no flushing, new parts etc seem to have any impact.... only thing never replaced as of today is the radiator... heat and a/c work great...

 

If and what that means, I don't know.

I can say with no reservation that I don't need to see a picture to know exactly what "proper" looks like on the gauge.
I've driven personally roughly 4-500k miles over 3 4.0L Jeeps... literally from the first to last mile. My dad's 94 XJ, my 00 TJ bought brand new, and my current 95.
The TJ never ran cold-ish... I don't recall my Dad's doing so either... I can ask him, only my 95 and apparently your 96 that I know of.

 

Install a Mopar thermostat. 83501426xxxx

 

That is what came out when the radiator was replaced for leaking, but temps were looking correct. Going to clean it up and reinstall this weekend. Also have a spare housing from a 4.0 Grand Cherokee soaking the grease off now. The first thermostat housing I ever replaced broke (1973 Dodge Dart slant six), so nice to have a backup.

 

Here is an obvious question... your 96 is new enough to only have the sensor in the t-stat housing and not have the gauge driven from the back of the head ? If so you also need to prove that the sensor is working correctly since single source will read exactly the same on the obd reader and the gauge. Either read with an infra red temp scanner or remove sensor and drop in a pot of boiling water and read the resistance. Should read 675 +/- 25 ish.

 

I don't think that was a thing until 97.

 

One sensor. Before starting stream read 95f, IR thermometer was within 3 degrees at fat end of housing. After a short drive both say 179.

 

Just to be totally clear... your 96 does NOT have the sensor for the gauge at the back of the cylinder head?? Are you 100% sure?... the back of the head one is really small and tucked waaaay in the back... easily overlooked in other words.

I was under the same impression as Spencer_P in that the gauge being driven by the CTS in the t-stat housing started in 97... I could definitely see a correlation to ODB type.. meaning ODB1 96's used the head sensor, ODB2's the CTS... but that's pure speculation on my part. I don't own an actual 96 though, so if you could answer this definitively I'd appreciate it greatly.

 

Regardless of the sort of academic curiousity... Clearly the most important temp reading is the one the computer gets so it can adjust fuel and all that good stuff. It's also not impossible that the actual gauge itself is not working perfectly... However, the ODB2 tool will tell you exactly what that temp value is that the computer receives, whether it's the *actual* temp or not... it's what the computer is using to do calculations so that's the certain way to monitor it if the primary concern is engine management rather than what the dash tells you.

 

Again, this lower than proper temp thing is exactly in line with what I see with my 95.... a new Mopar T-stat did NOT have any perceptible change. I don't regret swapping it, I'm just reporting what I observed FYI.

 

Anyway, I think we can eliminate the theory that the sender is reading exactly 15 degrees low, and if anybody wants to go with the theory that the IR thermometer is also exactly 15 degrees off, go right ahead.

No sender at the back of the head.

When the thermostat that came from the factory, that I cleaned off with PB blaster and is now soaking in Dawn and warm water, was last in this engine, it warmed up to 210F on the gauge and stayed there through just about anything (unless something else was broken, like the line to the overflow bottle).

 

Yeah, I concur you're reading the correct temp...

Thanks for checking on the 2nd sensor question... at least good to know for future reference.

I have never seen my current Jeep hold temp properly for any real stretch of time... it's always been wonky due to other known issues or runs cold like yours.... I'm hoping you find the answer so I know what I need to do myself...

 

Take a picture of the rear of the head driverside.

 

Still waiting for your closed loop video.
But mine starts in CL so it should be a short one lol.