Truck engine overheating AFTER being turned off?

Rexblaster
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Rexblaster
Hey y'all, looking for some experienced engine guys to give me an idea of what the heck is going on here. Truck is an 07 escalade ext with the 6.2L l92 that runs and stays perfectly at temp while engine is on. Coolant is filled to the cold fill line appropriately and using GM dexcool as is required by the manual. But for some weird reason, whenever it gets shut off after running for a bit the temps creep up and have gotten as high as 5/8's of the way to the max on the gauge. For a bit i thought my gauge was malfunctioning, till i realized that whenever i start the truck anywhere above operating temp i get a nasty knocking from the engine on startup. Should the fans be on more, thermostat malfunctioning, too low of pressure... anything? Really wracking my brain trying to figure out how it can stay at temp the entire time while running but creep whenever its shut off. Can give any extra info if yall have questions.. thanks!!
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FlickitFlat
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FlickitFlat 6/17/2021 4:58am
6/17/2021 4:58am
Every engine will get hotter once you turn it off and the radiator stops circulating. Your dirt bike does the same thing. Every motor. That being said, it sounds like you have a bad thermostat to me. It is nothing to change and see if it was the culprit, $10 at the most.
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Falcon
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Falcon 7/22/2021 8:54am
7/22/2021 8:54am
X2. Heat from the engine has to go somewhere when you turn it off, and it goes right where it's supposed to: the water. With no fan or wind across the radiator, there's nothing to cool it down, so the water temp increases.
KMC440
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KMC440 7/22/2021 1:04pm
7/22/2021 1:04pm Edited Date/Time 7/22/2021 1:06pm
Funny and true ... Henry Ford originally thought the heat of the engine (hot air rises as does hot water) would be enough to circulate the water through the engine and radiator. NOPE ... went through a few motors trying that out. Enter the water pump.... which needs to be moving the water along with a fan blowing on the radiator to truly cool the engine while it is not running.
(water pump is driven off the engine so those electric fans that stay running as you walk away from the vehicle don't do as much as they could)
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blusmbl
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blusmbl 7/22/2021 5:56pm
7/22/2021 5:56pm
If it knocks a little on warm restarts it might need higher octane fuel, but the behavior you're describing is totally normal. One of the standard cooling system tests for OEM's is to get a vehicle super hot at max trailer load, then shut it off and make sure the coolant doesn't boil over to the point of venting from the cap and leaking onto the ground.

KMC- I think the T's had no water pumps, but they did have a fan at least. 22 hp and 4.5:1 compression doesn't exactly put a ton of heat in the cooling system though!
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sumdood
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sumdood 7/23/2021 11:32pm
7/23/2021 11:32pm
We used to yank the thermostats out in our cars that ran too hot. Some guys would say “ That won’t work because the water won’t be in the radiator long enough to cool down“ but that never happened in my experience. The more flow the better and the faster you went the better if worked.

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