Air in the coolant system.

[DeLoreanMan82]

How all this started was her original valve cover gaskets were starting to leak oil. Ok, it has 329K original miles. So while in there I went to replace the whole coolant system, minus the heater core. Now this is when it all began. I even removed the water pump to see if the impeller was slipping and that was tight. Removed the thermostat to double check the position of the thermostat and the bleeder and that was fine. Even did a CO2 test and that was fine. Took it to a Jeep dealership and they flushed it and did a CO2 test and THAT was fine still. When I picked it up, I could hear the coolant flowing in the dash which tells me there is still air in the system. So I dug and dug and came upon a post about where people are still having air in the system and everything pointed to the thermostat that it should only be MOPAR. Hey, i'm not doubting them as I been working on cars for 30 years and this has wiped my ass and wouldn't be the first time this Jeep had an issue where I had to use a factory part and that was for the front drive shaft.

Coolant is flowing great, but looking at the bleeder of the MOPAR version looks different than the Dorman version.

When I called the dealer and explained the thermostat issue, they told me that they have issues like that with their Wranglers doing the same thing, using aftermarket thermostats. Customers putting in aftermarket versions, then overheating and then reinstalling a factory piece and TADA, problem fixed!

 

[DeLoreanMan82]

Dorman is never my first choice but with that said, I installed a Murray from O'Reilly. It's all they had and I needed it right away. Temp gauge always sits one tick below the halfway mark. I don't know if the thermostat is your problem. I'm not a very experienced mechanic, but it seems you've tried everything else. My gut tells me your water pump is flaky, and the impeller is slipping on the shaft.

Oh, and btw, her temp gauge ran at the same position as well. When driving there is no issue. It's when you come to a stop and yes, the electric fan works just fine.

 

[Steve1951]

You don't need to go to so much trouble; the cooling system bleeds itself if it is sound. Let me explain: Fill the header/Expansion tank to the cold fill level.
Start the engine, drive until it reaches operating temperature, which is just below the red line on the gauge. Remember the thermostat doesn't open till 90 degrees F.
Park the car overnight, or until it's cold to touch.
The coolant will be recovered from the tank, as long as there are no leaks and the filler cap hasn't been removed.
Top up the coolant. Done!
I always check the next morning, to be sure.

 

[Steve1951]

How all this started was her original valve cover gaskets were starting to leak oil. Ok, it has 329K original miles. So while in there I went to replace the whole coolant system, minus the heater core. Now this is when it all began. I even removed the water pump to see if the impeller was slipping and that was tight. Removed the thermostat to double check the position of the thermostat and the bleeder and that was fine. Even did a CO2 test and that was fine. Took it to a Jeep dealership and they flushed it and did a CO2 test and THAT was fine still. When I picked it up, I could hear the coolant flowing in the dash which tells me there is still air in the system. So I dug and dug and came upon a post about where people are still having air in the system and everything pointed to the thermostat that it should only be MOPAR. Hey, i'm not doubting them as I been working on cars for 30 years and this has wiped my ass and wouldn't be the first time this Jeep had an issue where I had to use a factory part and that was for the front drive shaft.

Coolant is flowing great, but looking at the bleeder of the MOPAR version looks different than the Dorman version.

When I called the dealer and explained the thermostat issue, they told me that they have issues like that with their Wranglers doing the same thing, using aftermarket thermostats. Customers putting in aftermarket versions, then overheating and then reinstalling a factory piece and TADA, problem fixed!

It is wise to test thermostats, even new, genuine, or replacement ones.