Fluctuating Coolant Gauge

steelerdude15 · October 27, 2023

5.3 with 55,000 miles. Before my old thermostat started to fail, my coolant temp gauge seemed to always stay right in the middle of the 210F line. I replaced the thermostat this past Saturday with a new GM one. Since then, my gauge is still hitting the 210 mark, but is now very slightly to the left instead of dead center. If I do a hard pull, the gauge will slightly move past the 210 mark without touching the next line, but immediately go back to where it was. I know this gauge doesn’t give an accurate temp reading. My scan tool shows my coolant temp is 207F to 216F while cruising at 55mph. It will go up to 223F if driven hard, but will immediately go back down to the temp range noted above. There aren’t any codes popping up. I also did a coolant change since the truck turned five years old this month. Am I fine or is there a problem?

CamGTP · October 27, 2023

It's fine. The stock OEM thermostats are usually better than the aftermarkets if you went that route. I installed an aftermarket one 2 years ago and it slowly started to fail, it would stick closed and run warmer than it should before opening up. Then it would run 5-10 degrees hotter. It had a lifetime warranty so I just swapped it, it's been running right at the normal temps again since.

The temps you are seeing are fine for now, I wouldn't worry about anything until it started running cooler or even hotter than what you are seeing.