Wife’s JKU overheated so I started small and changed the thermostat. Nope. Moved to the water pump. Nope. Since she had issues with split heat between the drivers and passenger side I reverse flushed the heater core. Nope. I changed the heater core. Nope.

It still overheats after all the new parts and burping the system. It also only blows cold air when the heater is on. I switched the AC control unit with the one from my 2018 JKU. Didn’t change anything.

Only one of the two heater hoses is hot and once it starts to overheat it pushes fluid into the funnel attached to the radiator and it overflows. But no air bubbles.

WTH?

 

Seems like a tricky situation so starting with 2 very basic questions. If you pop the cap of the rad in the morning is the coolant right to the top there? Are you noticing any change in the coolant reservoir over time?

In regard to the heater, have you confirmed the blend door is actually working? Seems like this is not the HC since it has been replaced. Only other thing would be air in the HC that you're struggling to get out.

 

When I pop the rad cap I can somewhat see coolant. A simple squeeze of the upper hose and coolant rises to rim. No notice of any changes in the res.

 

I'm chasing this too. I'm about to update my thread. Nothing is adding up.

 

Literally the only thing left to change is the radiator.

 

Update: I got fed up and took it to my mechanic. Guess what it didn’t do…overheat. Dropped it off anyway to flush coolant. However, during their intake inspection it overheated. Diagnostics pointed to radiator so we replaced it. Now new operating temps are 208 - 215 which prior to all this the norm was under 200. At least it’s running, right.!?

note: my 18 JKU runs 190 - 200s

 

208 - 215 is normal to me. Actually, 222 is not abnormal. I've never seen mine running sub 200 unless it was freezing cold out.

 

Hey GirlDad, so changing out the radiator has cured your issues (for now) what do you suppose was wrong with the radiator? plugged up? leaking ? I'm glad your overheating problems are gone for now, any lessons learned from examining the old radiator might help the rest of us....

 

I honestly didn’t think it could have been the radiator since some of the initial signs pointed towards the heater core; heater blowing hotter on one side. I was reluctant to start with the HC due of the complexity so I started smallish. After changing the thermostat, water pump and finally heater core I still had issues which I associated it with air since I had so much “open”. With little time to work on it and my wife wanting her Jeep back I brought it to my mechanic. They noticed a 60 degree difference between the upper and lower hoses and recommended changing the radiator. Lesson learned: bite the bullet and take it to your mechanic. lol