2017 Silverado 5.3 - Temp Gauge Fluctuation

[Mr. Pibb]

Need Help Please!!!!  I truly appreciate anyone that reads this long post.  Hopefully someone can help me figure this out.  

 

Bought my 2017 Silverado CrewCab LT Z71 new.  For 5 yr & 10 mo. the temp gauge sat at 210 with no issues and no variation. Then, in June 2023 the temp started rising about 10 degrees and would fluctuate from there back to normal. 

1. Thermostat was replaced, didn’t resolve the issue.  
2. Temp sensor was replaced, didn’t resolve the issue. 
    

Truck is well maintained, radiator/coolant flushes done a normal intervals with no issues found. 

 

Dealership has checked out this issue 3 times and says it’s operating as normal, temp fluctuation is normal.

 

I have been calling BS on this since June, how is this normal? Almost 6 years with no variance but now it’s normal?  

 

So here I am in October, with continued temp issues that are anything but “normal” The temp gauge has progressively increased, the gauge goes up to 245-250 then will drop back down to 210 and fluctuates between 210 - 230/235 as the drive continues.  

 

Things to note:

1. I have never had a Check Engine light, adding to the frustration. 
2. Coolant level doesn’t change, no leaks whatsoever.  
3. This temp issue does not happen when idling.  I’ve idled for 20-30 min both from cold and after driving with the issue happening, no fluctuation. 

 

I have thought through some other possible issues but then wonder could it be “this” when the issue is not consistent or throwing codes. 

• Are the active shutters not opening / operating correctly, that should throw the check engine light 
• Belt is loose, again should be a more consistent issue with sounds and other functions having issues.  
• Water pump going out, again I think that would cause more consistent issues and would overheat the engine.  
• Fan(s) going out, wouldn’t that be more of an issue when idling vs driving and would be a more consistent issue.  
• Could this be some other sensor, relay, electrical issue. 

Any help, experience, and/or suggestions you have on this issue are greatly appreciated. 

 

[rav3]

How many miles on it. Have any modes been done?

[Mr. Pibb]

No Mods, 97k miles

[mikeyk101]

Did you replace it with an aftermarket thermostat or an OEM one?

[Mr. Pibb]

OEM, for the Thermostat and Temp Sensor 

[mikeyk101]

I agree that something is going on. If you were hauling a trailer in some more challenging areas, the higher temps would make sense. But if you are just driving around in average areas, I agree that it's not normal. In my case, last winter, my OEM thermostat went bad and my dash gauge wouldn't get up to the 210⁰ like it had done for years even on the coldest days. I decided I wanted to change from the OEM 207⁰ to an aftermarket Motorad 194⁰ thermostat. I switched to a cooler one because I sometimes tow a toyhauler and had experienced some higher than normal temps especially in areas with steep grades and figured if the thermostat opened a little sooner, the radiator would help with keeping coolant cooler. It worked well for a couple months and the dash gauge showed the steady 210⁰ all the time. Then several months after installing, I experienced the motor running hotter than normal especially when running at higher speeds or accelerating a little faster than regular. I switched it out for an OEM 194⁰ that is found in several Corvettes and Cadillac CTS models and haven't had a problem since. Dash gauge normally stays at the 210⁰ except for occasional temp increases when towing toyhauler in more challenging terrain.

 

 

One thing I would mention is that the dash gauge is very generic. When it shows 210⁰, the coolant can actually be anywhere from 185⁰ to about 225⁰. So if it moves higher, it is already well past the 210⁰ temp. The best way to monitor the current coolant temps is through an OBDII reader. I use a BAFX Bluetooth reader and Torque Pro app on my phone.

 

But yours is odd. I'm wondering if maybe the replacement thermostat is defective? Any chance you are having an issue with your cooling fans running all the time?

[Mr. Pibb]

I had experienced the fans running even after the engine was off before the temp sensor change.  They still seem to be running more than usual but haven’t been running after the engine is off.