On a road trip with the wife. Our 2015 has been running great and the cooling system had a full service with a new tstat and mopar coolant about 6 months ago. 130k mi. Today, we were just putting around town early morning, not stop and go, and I noticed the car running hot. 65 degrees or so out. Car was running at 230. Drove about 3 miles to a park and it inched its way up to 250, but going down a few degrees, then up a few. Once the coolant temp light came on, I parked it.

We spent about 2 hours in the park and I came back to the car. Coolant level appeared good. Car has been running normally for months until now. It has not appeared to go above 220 in normal use today, hovering around 205-215 which is normal for the pentastar as I understand it.

so what on earth caused the random overheat? I made sure to get air out of the system when I did the work months ago. Speed of the car didn’t seem to affect the temp, so I don’t think it is a fan failure.

the only thing we did different was yesterday we drove up Roan Mountain, which is elevation 5.5k. Not sure if the elevation change did something but the car drove normally up and down the mountain and all last night.

 

Just to update this - the car has been relatively normal for a while and just started doing it again today. Some things I noticed - the temperature doesn't seem 100% related to what's happening. For instance, it seems to overheat most at slow to medium speeds. It seems to stabilized at highway speed but not 100% - sometimes it will go up but not related to climbing a hill. I actually saw it go DOWN when climbing a hill on the highway today. The fans seem to work normally - low is on constant and the high kicks on about 230. However, the high fan seems to only be able to MAINTAIN 220-230. It sat at idle for about 5 minutes with the temp sitting at 230 and it never dropped, even with the fan running full blast. Also of interest - I sprayed the condenser with cool hose water for a good minute and the temps didn't drop at all, which is really odd to me. I'm starting to think perhaps its a bad sensor? I'm at a loss on this as nothing makes sense...

 

Anybody have any thoughts on this? I've since replaced the water pump (old one looked fine) and did all coolant again with a long bleed to get all air out. Car ran normal for about a month but now on hot days is hovering around 220-235 and creeps up if I let it sit parked. Fans do operate normally. The one odd thing I noticed today is seeing the coolant overflow is nearly at the top. When I refilled everything, I put it halfway between the marks. I'm at a complete loss now unless we're looking at a blown headgasket, but if that was the case I would expect coolant level to be low in the overflow, not high?