2017 6.2L Running hotter than normal. Any ideas

schendela · March 24, 2024

So backstory..

8 months ago I replaced the coolant temp sensor as it had gone bad. Replaced it with a generic sensor from Oriellys. A month ago, same thing happened, replaced with same part.

During that 6 months we drove probably 15k, everything was fine, except yukon would never get up to 200. Chalked it up that the thermostat was stuck open, didnt really matter to us, we live in texas and again, wasnt causing any issues.

2ish months ago, the sensor went out again and figured while Im elbow deep in the engine bay, Ill replace the thermostat, again with some generic thermostat from o. Drove it probably 1500 miles before I noticed one day while driving to colorado that it was getting above 220. It would get to 225 but then go back down, just enough of a difference to move the needle on the guage. For the rest of that drive (300 miles) I logged the temps/speed/engine load on my phone. All was ok. Drove it back to Texas the next day, everything was fine the entire drive (1k miles).

Then today, we were in Dallas, not paying to much attention I saw the guage move and started up the scanner, saw it was sitting at 225, but would cool back down. Well driving home from dallas I wasnt able to go above 77mph or the yukon would sit above 230. Didnt matter what I did, any load on the motor would just cause the temp to go up and slowly work its way down. 50 miles from home I stopped at a car wash to wash the radiator thinking it might be clogged up and just not have good air flow.

Got home checked the upper hose and lower hose with a temp gun, 50 degree difference, so it seems to be working, but the problem still exists.

During idol, it stays around 216, but under any load the temps crawl up and slowly come back down.

Does anyone have any ideas? Im to the point where im thinking about running a 160 degree thermostat, as well as buying the GM temp sensor, but not sure. I wouldnt think its an air bubble in the cooling system, since it waited almost 1500 miles to show first signs, but then didnt do anything until roughly 3500 miles (after thermostat replacement)

Now Im no mechanic by any stretch, but I understand most things, so I dont know. I dont think I bled the system out as best as I could have, but again with the mileage after changing it I would have thought it would have shown up sooner.

No codes or anything either.

Let me know what you guys have.

Thank You!

CamGTP · March 24, 2024

A lot of aftermarket thermostat have problems like that. The OEM thermostats have been really hard to find right but I've had good luck with the thermostats from Napa.

I'd be trying to find and OEM or going with a different thermostat before getting too much deeper into it. Or just switch to a 180 degree thermostat. Don't run a 160 as that will be too cold and can cause a check engine light without tuning in some cases.