Resharp001,

99% certain all the air is out. Ran it with the defroster on constantly over ~150 miles this weekend. Highway, offroad, and up/down steep inclines. Squeezed the radiator hoses to help as well. Filled the reservoir/radiator up when low at first but it quit taking extra coolant right before my 150 mile trip. Is there anything else I haven't done to try burping it? I'd expect oil in the coolant or vise versa if it were a head issue as well. Don't know if I ever mentioned but the Jeep only has 114k miles as well...

The overheating was occurring before I did the coolant flush and replaced the thermostat. I did both to try and fix it, so I don't think either of those are the issue at this point. The water pump pulley felt fine when I just swapped the serpentine belt and other pulleys. No signs of leaking coolant anywhere. Fan seems to be running all the time when hot.

It almost doesn't seem like running the defroster even helps much, AND it was slightly overheating at idle the other night. There is no damage or changes to the radiator/airflow so this makes it sound more like a WP right?

 

I know you probably don't want to see this, but do an engine cylinder compression check. You could have exhaust gases getting into the coolant system when under heavy load.

Also, you don't have any geegaws cluttering up your grill, do you? The 3.6L in the JKs is very sensitive to plastic grill guards, etc. I know this because we did some testing on them before heading to Alaska. My friend wanted something to protect his AC condenser from rock damage on the Dempster and Dalton Hwys. A great idea. But after trying some of the cheap plastic grill guards, and finding that engine coolant temps ran about 20° higher than normal, we ended up using chicken wire.

 

When troubleshooting things I'm always looking for things that just stand out and this line right here is one of those things. IDK what you're idea of slightly overheating at idle is so I'll tell what I generally recall from my "test" experience few years ago. I let the jeep idle in the drive for a long time and several cycles as I was trying to determine "normal" fan activity. The fan on my '13 kicks on ~224° and it would run until the temp dropped back down to 210° at which point it would turn off and temps would creep back up and the cycle would continue. My fan kicks to high somewhere around 234° when driving. So, if you're getting up above 225° while idling in the driveway and the fan is kicking on then I'd think there is certainly restriction at the thermostat or radiator, or the WP isn't circulating efficiently.

I can never disagree with compression test as troubleshooting, though I do think combustion gas test with an inexpensive kit is a lot quicker, especially since you have to pull the whole intake to do compression tests on the driver's side of the 3.6L.

I replaced my water pump at 95k miles when I swapped my last radiator. It was just a preventative measure at the time as I had easy access when the rad was out. If you want to see a few pictures what mine looked like at that time there are a few in this thread. The WP itself seemed perfectly fine but there was a lot of pitting on the gasket that I thought was odd -

https://www.jk-forum.com/forums/stoc...nstall-354457/

I'm just a dude that does my own work on my vehicles, so I'm no certified expert. If I was having this issue my troubleshooting would look like this -

1) swap in a different thermostat, again. Observe if any change.
2) cheap combustion gas test like this ( https://amzn.to/3qRK8m1 ) only cuz it takes a couple mins and gives peace of mind
3) replace WP
4) replace radiator

When I bleed my system it typically takes me a couple mornings of topping off at the radiator cap after driving the previous day even when it seems it was 100% burped the day before.

I'll sit back and just monitor the thread and let others chime in so I'm not clogging it up.

 

Got it. I'll run the compression check and a coolant combustion check when I have some time soon.

I do have some stuff in front of the grille (winch, bumper, wire mesh bug guard) but it was never an issue for years. This only began happening within the past month. I'm also going to try removing the grille and driving around for a little to see if it has any effect but I'm suspecting not.

 

I guess my point would be if the temps are getting higher than normal in driveway at idle and with the fan kicking on, then it's not an airflow issue.

 

Ordered that combustion leak test kit. If I can rule that out then I'll check the thermostat again (hard to believe two would be bad but I'll look into it), swap the WP, then radiator. Thanks for all your help and input, I really appreciate it!!! I'll keep you all posted on the results.

 

You said 2 thermostats, were they mopar or generic, I read somewhere that some of the generic ones restrict flow vs the mopar.

 

Original one was a MOPAR unit. I replaced it with a Duralast unit from Autozone that had a decent number of good reviews. No difference.
I suppose it's possible they were both bad (or the MOPAR one went bad and the Duralast one is restricting) but I'm fairly confident it's not the thermostat. I'll still check it out again if the combustion leak test is negative.

 

Hi
I have similar problems with the green rubicon (profile picture) change thermostat, check radiator, change head cylinder gaskets..........
Then by luck (2 years after) found my problem..... was the cabin radiator (heating system) was in very bad shape, canīt found an original one in my city, but replace it with a hyundai one (same size) and problem solved.
Actually I have a 2018 Sahara but the actual owner of the green one is a friend of mine and never again have temp problems.
Cheers

 

I was gonna recommend the same as i just kinda went through the same issue after another forum member mentioned that Autozone and Oreillys thermostats are prone to failing, or not functioning correctly out of the box. In my case, the autozone brand wouldnt open fast enough to control the temps and i would see the same temps the OP is seeing. Temp would creep all the way up to 245 degrees before it fully opened and allowed flow. I went with a MOPAR brand, did three or four bleed cycles and now i dont see over 226 in the worst conditions but around town, in 100 degree ambient, it will hover around 212 degrees, which i am fine with. Thats with a big ol winch blocking airflow as well.