Temp question

[15 Z71]

Hopefully some can help me. I have a 2015 gmc sierra 1500 5.3. The last few days I have noticed that the temp gage go's up to 210 then starts to fall a little. It has always ran dead on 210. It drops 1 or 2 marks then goes back up to 210. I assume this is the thermostat going bad? Just looking for some advice before I change it and hope that's it. Thanks.

[CamGTP]

Could be sticking open a tad but what you see isn't a huge problem. If you watched the temps with a scan tool or OBD2 code reader with live data it probably still shows 200-215 degrees like most do.

 

If it's running down at 180-190 all the time then I'd change it out because it's for sure sticking open then.

[15 Z71]

Would this going and down a little cause me to get worse mpg? Seems like I went from 18 or so mpg to a little of 16 now. 

[CamGTP]

No, that little change in running temp wouldn't cause a drop of fuel mileage like that.

 

Colder weather, driving style, remote starts and extended idle time for sure would though. My fuel mileage always drops in the winter months because I only drive city speeds.

[txab]

Don't forget fuel blends changing over for winter also as a possibility

[Yotaman]

Do a search for cycling thermostat Bad news is it can cause your radiator to crack and leak good news is you noticed it and can replace it. GM has a new updated part be sure you get the right part.

 

Yotaman

Edited December 8, 2021 by Yotaman

[15 Z71]

8 hours ago, Yotaman said:

Do a search for cycling thermostat Bad news is it can cause your radiator to crack and leak good news is you noticed it and can replace it. GM has a new updated part be sure you get the right part.

 

Yotaman

I had the radiator and thermostat replaced about 5 years ago because it cracked and had wrong thermostat in it. I assume it has the updated one now?

[mikeyk101]

3 hours ago, 15 Z71 said:

I had the radiator and thermostat replaced about 5 years ago because it cracked and had wrong thermostat in it. I assume it has the updated one now?

I think this would depend on who did the work. If it was a GM dealership, you will most likely have the proper thermostat as GM usually frowns on dealerships installing modified parts.

[15 Z71]

10 minutes ago, mikeyk101 said:

I think this would depend on who did the work. If it was a GM dealership, you will most likely have the proper thermostat as GM usually frowns on dealerships installing modified parts.

Yep it was the GMC dealer I bought it from. The one that came in it from the factory only made it about a year then cracked the radiator.