Engine cooling issue with 6.2

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schendela

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So after reading the below thread 8 months ago, the following has occurred.

8 months ago I replaced the coolant temp sensor as it had gone bad. Replaced it with a generic sensor from Oriellys. A month ago, same thing happened, replaced with same part.
During that 6 months we drove probably 15k, everything was fine, except yukon would never get up to 200. Chalked it up that the thermostat was stuck open, didnt really matter to us, we live in texas and again, wasnt causing any issues.

A month ago, the sensor went out again and figured while Im elbow deep in the engine bay, Ill replace the thermostat, again with some generic thermostat from Oriellys. Drove it probably 1500 miles before I noticed one day while driving to colorado that it was getting above 220. It would get to 225 but then go back down, just enough of a difference to move the needle on the guage. For the rest of that drive (300 miles) I logged the temps/speed/engine load on my phone. All was ok. Drove it back to Texas the next day, everything was fine the entire drive (1k miles).
Then today, we were in Dallas, not paying to much attention I saw the guage move and started up the scanner, saw it was sitting at 225, but would cool back down. Well driving home from dallas I wasnt able to go above 77mph or the yukon would sit above 230. Didnt matter what I did, any load on the motor would just cause the temp to go up and slowly work its way down. 50 miles from home I stopped at a car wash to wash the radiator thinking it might be clogged up and just not have good air flow.

Got home checked the upper hose and lower hose with a temp gun, 50 degree difference, so it seems to be working, but the problem still exists.

During idol, it stays around 216, but under any engine load the temps crawl up and slowly come back down.

Does anyone have any ideas? Im to the point where im thinking about running a 160 degree thermostat, as well as buying the GM temp sensor, but not sure. I wouldnt think its an air bubble in the cooling system, since it waited almost 1500 miles to show first signs, but then didnt do anything until roughly 3500 miles (after thermostat replacement)
Now Im no mechanic by any stretch, but I understand most things, so I dont know. I dont think I bled the system out as best as I could have, but again with the mileage after changing it I would have thought it would have shown up sooner.
No codes or anything either.

That was last night on the drive home, roughly 180 miles.
Today, I have taken the top shroud off to inspect the radiator, which does appear to be dirty, but doesnt seem excessive. I have removed the upper radiator hose, and everything seems to be full of coolant. Purge tank is full as well. When I removed the cap, it leaked out, making me think that the system is at proper levels in both rad & engine.

Any ideas?

Let me know what you guys have.
Thank You!
 

Marky Dissod

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Just thinking:
burp it again (had to burp my LT1 Caprices several times over 7 days to fully burp all air from coolant)
replace temp sensor with genuine GM
replace thermostat with genuine GM
...
does your transmission have the updated thermostat / temp control?
You may want to check your ATF temps when the coolant temp sensor reports 221F.
 
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schendela

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Just thinking:
burp it again (had to burp my LT1 Caprices several times over 7 days to fully burp all air from coolant)
replace temp sensor with genuine GM
replace thermostat with genuine GM
...
does your transmission have the updated thermostat / temp control?
You may want to check your ATF temps when the coolant temp sensor reports 221F.
I didnt think about checking trans temp during this whole ordeal. But the trans temp has always, atleast on the gauge looked like it wasnt working properly either. That is something Im going to have to look into, but I dont think my bs little scanner can look at the trans temps, atleast not live/log it.
 

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Are you reading the engine temps with a scanner? If so, ignore what the gauge says until you know it's accurate.

We've seen many issues with the aftermarket ECT sensors; at this point it might be wise to use an OE (not "OEM") sensor.

OE = Original Equipment = what originally came with your vehicle
OEM = Original Equipment Manufacturer (who know if this mfr. made this particular part as OE?)
 
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schendela

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Are you reading the engine temps with a scanner? If so, ignore what the gauge says until you know it's accurate.

We've seen many issues with the aftermarket ECT sensors; at this point it might be wise to use an OE (not "OEM") sensor.

OE = Original Equipment = what originally came with your vehicle
OEM = Original Equipment Manufacturer (who know if this mfr. made this particular part as OE?)
Yes all temps have been read with a scanner not off the gauge.
How do you know what originally came with the vehicle? I ask as I bought this yukon at 90k. I have put two of these sensors in myself in the past 8 months. I would assume the GM genuine sensor, would be the most ideal swap at this point?
 

Marky Dissod

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How do you know what originally came with the vehicle? I ask as I bought this yukon at 90k.
I have put two of these sensors in myself in the past 8 months.
I would assume the GM genuine sensor, would be the most ideal swap at this point?
So long as you don't buy it from scamazon, yes, GM Genuine / AC Delco / Delphi
 
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schendela

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Update,
burped the system again, seemed to have everything full like it should be. Went on a test drive, again temps raised past 230, highest it hit was 237 when I decided to just coast the vehicle for a bit to let it cool down (roughly a mile from my house). By the time I got back to my house it was sitting around 217 and then I checked the hoses with a laser therm. and temps were roughly 201 on the thermostat side and 149 on the lower hose(at inlet to water pump).
All metal like heads and things were temping at 210-220. Fans were on and blowing air. It seems to be correct, but temps still are doing "dumb things".
I have ordered a genuine temp sensor, so we will see if this is a faulty sensor or not. After that, I think it might go to a dealer/shop as Im at a loss. All things say it should be good, but Im sure Im missing something.
 

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Update,
burped the system again, seemed to have everything full like it should be. Went on a test drive, again temps raised past 230, highest it hit was 237 when I decided to just coast the vehicle for a bit to let it cool down (roughly a mile from my house). By the time I got back to my house it was sitting around 217 and then I checked the hoses with a laser therm. and temps were roughly 201 on the thermostat side and 149 on the lower hose(at inlet to water pump).
All metal like heads and things were temping at 210-220. Fans were on and blowing air. It seems to be correct, but temps still are doing "dumb things".
I have ordered a genuine temp sensor, so we will see if this is a faulty sensor or not. After that, I think it might go to a dealer/shop as Im at a loss. All things say it should be good, but Im sure Im missing something.
we are seeing multiple multiple reports of these presumably aftermarket sensors and thermostats being bad out of the box or within a short period afterwards.
particularly on the K2xx (2015-2020)
I would def recomend original from dealer or legit retailer.
just keeps coming up almost weekly....... and like you people are replacing them again and getting the same results -failure
 
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schendela

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Use one of the online GM parts sites -- gmpartsgiant, gmpartsdirect, etc. Enter your VIN and you can find the OE part numbers for purchase there or for searching other parts places.

Like this (but that may not be your SUV): https://www.gmpartsgiant.com/parts-...front_cover_cooling.html?filter=(e=L86;t=MYC)
1711310751493.png
This seems to be of concern, the thermostat is discontinued. Im sure that is just that model for some reason, but still strange to see discontinued on a thermostat.
 

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