Another Overheating Thread

So I put the old coolant temp sensor back in, put yet another thermostat (third in a year) in and the went through the bleeding process again. Drove at highway speeds for 30 minutes and didn't even get hot enough for the fan to kick on. The code was still in so I did the key dance as stated above and it actually cleared the code so it must have been the faulty thermostat code. In conclusion the thermostats on these are junk. Check that first any time you have an issue. Thanks everyone for your help, it's much appreciated!!
 
Now my Jeep is throwing a code after changing the Coolant Temp Sensor. Of course the thermostat isn't opening now because of this. What next?? I don't have a code reader
You really cannot work on modern cars without a code reader. For a JK, download JScan and order one of the suggested OBDII dongles from Amazon. It'll cost you less than $100 and you'll have required information.
 
Glad you got it resolved.
Now, get yourself and OBDII dongle, as mentioned earlier and download the JScan app.

This is the one a lot of us have:

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This and the VIN license for the app will cost you less than the t-stats you replaced.
 
So I put the old coolant temp sensor back in, put yet another thermostat (third in a year) in and the went through the bleeding process again. Drove at highway speeds for 30 minutes and didn't even get hot enough for the fan to kick on. The code was still in so I did the key dance as stated above and it actually cleared the code so it must have been the faulty thermostat code. In conclusion the thermostats on these are junk. Check that first any time you have an issue. Thanks everyone for your help, it's much appreciated!!


What brand was the T-Stat, some have had issues with ones not OEM working right?
 
I had the same issue. I've been battling overheating issues for over a year with my 2012 jku rubicon. Especially in summer in Phoenix and going uphill it was running 240+ and i couldn't drive faster than 60 mph. First i replaced the radiator. Then the thermostat was replaced. No change so i kept going. Replaced the waterpump and even the transmission oil cooler. Took the winch off. Nothing helped. Since it was only happening at higher speeds and it was fine at lower speeds i didn't suspect the thermostat. Especially since it was replaced.
I had the engine and cooling system tested and the mechanics said everything was fine. So as a last resort i decided to remove the internal part of the thermostat. It's really simple to do and you'll be able to see if the thermostat is the issue. After this the car was running normal Temps. Apparently the new thermostat that was installed was faulty out of the box. I just threw a new duralast (motorad) thermostat in there since i couldn't get my hands on a mopar one. And voila. Problem solved.
These thermostats are crap and usually the problem. Suggest taking it out and testing it that way.
I hope this helps you and other people.
 
Make sure you purge air through the bleeder screw on the thermostat housing also. If you don't you may still get air In the system.
 
I’m having the exact same issue. I originally got the P0128 code. Silly me cheapened out and got the auto zone aftermarket tstat (forgot what it was maybe Murray one) and been having fluctuating temp gauge issues jumping above half way (Highway 60mph) mark till the high fan comes on (summer time is bad) it was on a lot. I’m too the point where I’m just gonna have Jeep put the OEM one and be done with it. . Thanks for this thread to confirm what I need to do. I’m so sick of having to constantly worry and watch the gauge lol.

Now I need to find out why my brake light randomly comes on for 5-10secs then goes off. My brakes pads aren’t bare yet but are on their last leg (20-25% left).