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Discussion Starter · #1 ·
2012 silverado 5.3 vortec started over heating slightly so I replaced the thermostat but didn't help. At low rpm it goes up to 220 ish get it past 2000rpm and the temp comes down to 210. Anti freeze tests out at -40 + so it's good , any ideas?
Forgot to say both fans are running fine and no leaks either.
 

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Running low RPMs, in slow traffic, outside temps greater than 90, with the AC on? Mine will overheat a little above normal in those conditions. Just a thought.
 

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Is the radiator blocked up with bugs or gunk?
The only thing I could think of is the fans aren't able to pull enough air across the radiator.
 

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What I was thinking or you sucked a newspaper/plastic bag/debris and it is obstructing flow. Just pulled debris out of the wife's car she was complaining the AC would not cool very well. She had styrofoam, palm tree debris, and piece of just road trash all up in the air inlet for the heat exchangers. I have always been paranoid about that seeing grocery bags on the road I always check my rear view mirror when I run over them to make sure I did not suck it up.
 

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Discussion Starter · #6 ·
Dommieboy said:
Is the radiator blocked up with bugs or gunk?
The only thing I could think of is the fans aren't able to pull enough air across the radiator.
No it's all clear , I was going to replace the coolant sensor next.
 

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2010 Silverado LS WT RCSB 4.3 v6
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I doubt the coolant temp sensor is the fault. Sounds like it's doing it's job just fine. With it overheating at idle tells me that you have some kind of restriction in the coolant flow. No way it should be overheating just sitting. Unless of course the fans are not running properly or there is some other mechanical problem such as the water pump.

How many miles on it? Have ever swapped out the Dec-cool or at least changed it? I got the Dex-cool out of my truck first thing after I bought it a few months ago.
 

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Discussion Starter · #9 ·
I watched a youtube video and someone had a faulty tensioner pully , it wasn't keeping enough tension on the belt gonna look at that too.
 

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Discussion Starter · #10 ·
Figured I'd keep this going it might help someone else. Pressured tested the system held pressure no leaks, I'll be doing a flush next see what goes.
 

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The flush could help. Maybe verify the actual temps with a scanner? My dash gage shows 210*F and my scanner shows 192*F.
 

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Discussion Starter · #12 ·
Ok this is giving me a headache , flushed and installed new hoses took it down the street and the temp now goes up to 235 from around 220. No antifreeze in the oil no oil in the antifreeze , water pump maybe?
 

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2010 Silverado LS WT RCSB 4.3 v6
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What does it do at idle now? Try removing the thermostat and run without one to see where the temp goes. I took an old thermostat and removed the guts so I would have the o ring to flush my system.
 

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Discussion Starter · #14 ·
temp started creeping up like before at idle took it for a ride and it went up to 235
 

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Discussion Starter · #15 ·
Forgot to say the coolant that was flushed out looked fine no discoloration or crud came out.
 

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2021 Custom Trail Boss 5.3 6L80E
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Under higher rpm's it goes back to 210 , also I tried burping some more air out and it doesn't go up to 235 now just 220ish like before.
My experience has been that if the engine runs cool on the highway but hot in the city, then the fans aren't working or turning on if their electric. If it runs hot all the time, then it's the radiator or water pump.
 

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Discussion Starter · #19 ·
My experience has been that if the engine runs cool on the highway but hot in the city, then the fans aren't working or turning on if their electric. If it runs hot all the time, then it's the radiator or water pump.
Fans are working so looks like a water pump or radiator ? When it comes to these any brands to stay away from ?
 

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Fans are working so looks like a water pump or radiator ? When it comes to these any brands to stay away from ?
I would probably replace the radiator with something reasonably priced, not the cheapest. You are running a 50/50 blend of antifreeze and water, right? The glycol alone is not a good heat transfer agent but more for freeze protection and to raise the boiling point. You probably know that already but just mentioning it.

Not disputing it with you but how are you making the determination that the fans are working properly? Are they electric or engine driven with a fan clutch?
 
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