Engine heating up to 235-245F

[David russ]

I have a 2020 GMC 1500 SLT 3.0 Duramax that I bought new. I have driven the truck for 4 years with no issues and only have 32,800 miles on it. I moved to Virginia from Tennessee august of 2024 and about two months later started experiencing my engine temperature spiking from its normal 210F up to 235-245F. I was concerned and took it to two dealerships where both keep telling my this is normal and that the engine is running within it’s operating temperature. I haul a 16 foot enclosed trailer for my business and after doing so I notice a strong burning coolant smell after just a 15 miles drive with a small load in the trailer. The dealerships are telling me that since there are no codes showing up that it is fine and that I should continue to drive it. I really don’t want to damage my engine by having it spike in temperature so much and before August I had never seen the temperature go above 210F. Any help would be great as they are suggesting to start replacing parts randomly until they can fix the issue “even though they stated nothing was wrong” and I’m not willing to pay for replacing parts just to do a process of elimination. 

[newdude]

13 minutes ago, David russ said:

I have a 2020 GMC 1500 SLT 3.0 Duramax that I bought new. I have driven the truck for 4 years with no issues and only have 32,800 miles on it. I moved to Virginia from Tennessee august of 2024 and about two months later started experiencing my engine temperature spiking from its normal 210F up to 235-245F. I was concerned and took it to two dealerships where both keep telling my this is normal and that the engine is running within it’s operating temperature. I haul a 16 foot enclosed trailer for my business and after doing so I notice a strong burning coolant smell after just a 15 miles drive with a small load in the trailer. The dealerships are telling me that since there are no codes showing up that it is fine and that I should continue to drive it. I really don’t want to damage my engine by having it spike in temperature so much and before August I had never seen the temperature go above 210F. Any help would be great as they are suggesting to start replacing parts randomly until they can fix the issue “even though they stated nothing was wrong” and I’m not willing to pay for replacing parts just to do a process of elimination. 

 

 

Are you watching this on the gauge on the dash or actual live engine coolant temperature data from say a code scanner that has live data ability or an aux. gauge monitor like the Edge Insight CTS3 or Banks iDash?  

 

 

Edited February 6, 2025 by newdude

[Kevin0311]

time for a coolant flush 5yrs, but i'm betting sticking thermostat (s) not opening all the way, not sure if the 3.0 has two like the 6.6. Not going to show code unless out of parameter (high/low temp) 

[newdude]

7 minutes ago, Kevin0311 said:

time for a coolant flush 5yrs, but i'm betting sticking thermostat (s) not opening all the way, not sure if the 3.0 has two like the 6.6. Not going to show code unless out of parameter (high/low temp) 

 

 

3.0 Duramax doesn't even have a thermostat.  

[Kevin0311]

How does that work with no thermostat? on demand waterpump?

 

never mind i just read about it the thermal management

Edited February 6, 2025 by Kevin0311

[newdude]

On 2/6/2025 at 3:39 PM, David russ said:

I have a 2020 GMC 1500 SLT 3.0 Duramax that I bought new. I have driven the truck for 4 years with no issues and only have 32,800 miles on it. I moved to Virginia from Tennessee august of 2024 and about two months later started experiencing my engine temperature spiking from its normal 210F up to 235-245F. I was concerned and took it to two dealerships where both keep telling my this is normal and that the engine is running within it’s operating temperature. I haul a 16 foot enclosed trailer for my business and after doing so I notice a strong burning coolant smell after just a 15 miles drive with a small load in the trailer. The dealerships are telling me that since there are no codes showing up that it is fine and that I should continue to drive it. I really don’t want to damage my engine by having it spike in temperature so much and before August I had never seen the temperature go above 210F. Any help would be great as they are suggesting to start replacing parts randomly until they can fix the issue “even though they stated nothing was wrong” and I’m not willing to pay for replacing parts just to do a process of elimination. 

 

 

 

OP if you are still alive, 230-240F I've seen before on these 3.0 Duramaxes empty even.  Most of the time when those coolant temps occur its during regen or heavy loads.  

[Tinman623]

Check your grille shutter ! They tend to stick from dirt, salt etc. Make sure they are opening properly . My 2022 has upper and a lower shutters.