New thermostat overheating

[MAGAlomaniac]

2015 Tahoe lt. it was not coming up to temp so I replaced the thermostat and coolant temp sensor. Now it gets hot(220 -260) and the hose coming off the thermostat remains cool. I’ve got a Chevy thermostat on order. What else could this be?

 

[B-train]

Have you run it with the overflow cap off until the thermostat opens? Try squeezing the upper hose while running to see if you. An encourage any trapped air to move out. Lastly, double check with an IR temp gun on the upper hose, lower hose, and other coolant hoses to see what they are running for temps.

 

[OR VietVet]

What @B-train said. Sure sounds like that. Plus, get a better thermostat and then get the air out of it. Going to 220 degrees, is not worrisome to me but 260 is...

 

[Marky Dissod]

Going to 220F is not worrisome to me but 260F is...

With aluminum heads, I start looking to pull over @ 221F, by 230F I better have pulled over already.
Part of my pcm's tune is that it starts acting like it's already overheating @ 230F, to buy time.

 

[k_arnold72]

Did you possibly get a thermostat with a different temperature rating? If you get a lower temp thermostat without adjusting everything to work with it, this can be the result. Has happened to me before. If you have the oem spec 207⁰, disregard.

 

[MAGAlomaniac]

Have you run it with the overflow cap off until the thermostat opens? Try squeezing the upper hose while running to see if you. An encourage any trapped air to move out. Lastly, double check with an IR temp gun on the upper hose, lower hose, and other coolant hoses to see what they are running for temps.

I heard since the reservoir is the high point it will self burp. I tried bringing it up to temp with the cap off, no air came out. The upper hose never got hot even after the temp went over 220. The lower hose was hot to the touch. It’s got to be the thermostat right?

 

[OR VietVet]

Thermostat has to open to get heated coolant to transfer to radiator.

 

[B-train]

With a hot lower hose, you have a blocked thermostat. Replace with GM OE Parts

 

[Fless]

Back up a minute... why was the coolant temp sensor changed? Are we sure that that new one is reporting correctly?

 

[89Suburban]

You can’t just burp these out at standard idle. You need a few good random mid range revs to get the heater lines totally purged.