Do I really need a new thermostat?

R

Rookie-Vet91

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Oct 21, 2021
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My 2018 Silverado with 112.5k miles is not reaching the proper engine temperature when the heat is on. It will run between 160-180 degrees. When the heat is off, it will run 210. With the a/c on it will run 210.

My question is, do I really need to get a new thermostat? Besides not getting the hottest air circulating in the cab, if I do nothing, will any damage occur? A local shop quoted me $350-$400 to fix this.

What are your thoughts?
 
Rookie-Vet91 said:
My 2018 Silverado with 112.5k miles is not reaching the proper engine temperature when the heat is on. It will run between 160-180 degrees. When the heat is off, it will run 210. With the a/c on it will run 210.
Click to expand...
This is the same thing my Durango did when it had a bad thermostat.
 
spasm3 said:
Are the electric fans working ? Cutting off and on?

Are you looking at temps from the dash, or a scan tool?
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If I remember correctly, the fans are working. What would it mean if they are or are not working in terms of the thermostat working properly?

Temps are read from the dash gauge needle.
 
Rookie-Vet91 said:
If I remember correctly, the fans are working. What would it mean if they are or are not working in terms of the thermostat working properly?

Temps are read from the dash gauge needle.
Click to expand...
Just wondering if they were running all the time. If you are reading from the dash , the temps might not be that accurate and the temps depending on where the dash sensor is, may be even lower, confirming a bad thermostat. I've had lower temps on a scan gauge than the dash needle.
 
Propflux01 said:
Do you notice a corresponding reduction in heat temp in the cab? If so, thermostat time.
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I haven’t noticed a significant difference in heat output. I just started using the heat in the mornings, so I’m trying to recall what it felt like last time I used it earlier this year.
 
Rookie-Vet91 said:
I haven’t noticed a significant difference in heat output. I just started using the heat in the mornings, so I’m trying to recall what it felt like last time I used it earlier this year.
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Well, I see you stated in your initial post "Besides not getting the hottest air circulating in the cab", tells me it is stuck open. I'm betting it's taking longer to warm up generally, as well. As far as damage, it will wear the cylinder walls quicker because of the excess fuel (think choke stuck on longer). If you plan on keeping the vehicle, I'd spend the cash and change it. Probably coolant time anyway.
 
Do it yourself and save $$$$. A good time to also replace the coolant.

With the thermostat being of low cost , that is always a good start when the engine isn't running at the correct temperature.
 
I think it’s worth a try. The vehicle is not reaching operating temp. I used to wonder as a kid, how is it that engineers design a radiator/cooling so the engine reaches xxx degrees F? My dad said they don’t per se it’s the job of the thermostat. Say one car same engine has HD cooling. Other has a standard radiator yet they both stay at same temp…thermostat partially closed

Otherwise wouldn’t the HD cooled vehicle run cooler under normal driving…
 
I changed the thermostat on my 2016 Sierra last winter. The part was maybe $70 and tool me less than one hour in my garage. It's right on top, easy to get to. 4.3 and 5.3 engines use the same part and it is in the same location.
 
Hmm. Have you ever changed the fluid, and flushed out the radiator?. Or given the fins a good cleaning?. I've only changed out a thermostat if it didn't get the engine hot enough, or caused the engine to overheat. Has the radiator ever been changed?. If it's a aftermarket one, it might have a larger capacity which doesn't allow the engine to maintain proper temp under all conditions.,,
 
Donald said:
Some consider the thermostat a maintenance item. Just get a new OEM or Stant one.
Click to expand...
Stant was bought out by Motorad and shut down.
motorad_001.webp
 
BigCahuna said:
If it's a aftermarket one, it might have a larger capacity which doesn't allow the engine to maintain proper temp under all conditions.,,
Click to expand...
Larger capacity on an aftermarket radiator??? I only see that happening if you went out of your way for it, or if you bought the radiator for towing package that your vehicle didn't come with.
 
zzyzzx said:
Larger capacity on an aftermarket radiator??? I only see that happening if you went out of your way for it, or if you bought the radiator for towing package that your vehicle didn't come with.
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Being I know nothing about your vehicle, if you bought it new or used, or if it had been wrecked and repaired. I was trying to figure out what could be going on with it. You didn't say if the cooling system had been serviced, so like everyone else I was just throwing darts. If your vehicle has electric cooling fans, and they weren't working properly, it's possible you might think there's something wrong with the radiator. My friend who lives in Vegas thought there was something going on with his car, because it was running hotter than when he lived on the east coast. Once the temps remained under 100, it was like when he was here. I personally feel it would suck to spend money on parts that absolutely did nothing to correct a perceived problem. But that's just me.,,,
 
My last experience with a cooling system concern with a GM product was fixed by a PCM reflash
Look into TSBs

After that, I'd consider an OE thermostat and fresh coolant at this point in its life
michaelluscher

Post in thread 'Cooling fan strategy on a 2020 XT4'

PXL_20230118_042636772.jpg

It's perfectly capable of getting and staying up to temp now
I think I know what happened
Ice/debris/malfunction of the grille shutters sent it into some kind of panic/default limp home mode, keeping the fan on full blast, blunting warm up and heat performance
Or, it's an intermittent issue (position sensor/motor) issue with the shutters, that only manifests in severely cold weather
I've been able to open and close the shutters with bidirectional control many times, with no issue
The coolant being 8oz low was unrelated IMO 🤷‍♂️
I've finally got an appointment at the dealer...
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