2017 Silverado 5.3 - Temp Gauge Fluctuation

[Jonboy747]

Could have a air pocket or a sticking thermostat 

[Yotaman]

FYI may help someone down the road. So my new Thermostat I put in a few years ago started wandering low a bit so I decided to switch again. This time I bought a Dorman Brand from Amazon. It looked identical to the GM one. I put it in and thought all good but then I noticed a few days later that it was wandering on the higher than 210 side. So I hooked up my OBD2 scanner and found out like said at 185 degress F on the scanner the truck temp gauge hits 210. At about 217 on the scanner, it moves slightly above 210. My temp was swinging between 201-221 it would never stay long about 210 truck gauge. So I went to the dealer and bought a AC Delco Gold thermostat for about 130.00(I think you can get this same one on Amazon for about half) but I did not want to wait. I installed it and now my temp swing is between 205-212 or thereabouts and truck gauge stays on 210. The AC Delco looked just like the Dorman down to the made in China stamp.

Now I figure like most everything else quality is a crapshoot, and the Dorman was bad but to be fair I did leave the radiator reservoir open till the thermostat opened and ran the heater full blast so It may be possible the Dorman was not the problem but kinda think it was....... Hope it may help someone down the road.

 

Yotaman

Edited December 17, 2025 by Yotaman

[mikeyk101]

I learned the hard way about going with an aftermarket thermostat. My OEM one went almost 7 years before giving me a problem. I went with a lower temp (194⁰) Motorrad replacement. That only lasted a few months before starting to stick closed or partially closed. I went back to a GM but a 194⁰ thermostat and it's been working great ever since.

Edited December 18, 2025 by mikeyk101

[Racer311990]

To diagnose temp issues on these trucks, you really need a scanner. The $30 bluetooth ones on the jungle website are perfect. It graghs the coolant temp for you. You can actually watch the thermostat open and close. You will know immediately what the problem is.