Weird cooling system cool down vortec 5.0

[Erik the Awful]

I highly recommend this funnel for bleeding the coolant on any vehicle, but between this and your other post if you truly have a blown head gasket you'll need to fix that first.
www.amazon.com/Lisle-24680-Spill-Free-Funnel/dp/B00A6AS6LY

 

[Schurkey]

If it doesn't vent into the recovery bottle when the engine RUNS, it's not a failed head gasket.

 

[L31MaxExpress]

Sounds like heat soak based expansion to me. When you shut it off the cooling system ceases to function but the hotter cast iron is still dumping heat into the coolant. The coolant expands as it is heated and with the radiator already being pressurized that expanding coolant has to go somewhere.

 

[Schurkey]

I'm suspecting that the problem is made worse by a weak antifreeze/antiboil solution. The coolant is near boiling to begin with, then it heat-soaks and vaporizes.

But I haven't heard back on his antifreeze protection level, so that's just a guess.

 

[L31MaxExpress]

I'm suspecting that the problem is made worse by a weak antifreeze/antiboil solution. The coolant is near boiling to begin with, then it heat-soaks and vaporizes.

But I haven't heard back on his antifreeze protection level, so that's just a guess.

Agree, weak antifreeze and high operating temperature of a stock thermostat would allow the coolant to flash to steam.

 

[McSweeney]

Yea i see what you guys are saying, it does just seem like its due to the coolant being heated after shutting down, however it happens as soon as i shut the engine off so i dont know. A coolant flush obviously couldn’t hurt so ill plan on that, been so busy working ill try and test the coolant to see what my protection level is. I bled all the air out when I replaced those parts but its been so long now it probably would have burped up any remaining air by now. As long as ive had the truck its never overheated, went above normal temp once but luckily i was pulling into the driveway so i was able to shut it right down. That was last summer

 

[Schurkey]

it does just seem like its due to the coolant being heated after shutting down, however it happens as soon as i shut the engine off so i dont know.

Let us know about the freeze/boil protection of your coolant.

A coolant flush obviously couldn’t hurt so ill plan on that,

I like the Prestone flush-and-fill kits. BUT you still need to pull the block drains--on the small-blocks there's a steel/iron plug on the driver's side, and the knock sensor is the plug on the passenger side, just ahead of the starter. This releases the flush water trapped in the block, and allows (at least some of) the debris in the cooling system to escape.

ill try and test the coolant to see what my protection level is.

Good plan.

I bled all the air out when I replaced those parts but its been so long now it probably would have burped up any remaining air by now.

Yup. The high-point for coolant is the rad fill neck, any air in the system burps out the first time the thermostat opens. That air is seen as "low coolant level" in the radiator. If a person maintains the coolant level in the overflow bottle, even a somewhat low coolant level in the rad will burp the air out of the rad, and draw in coolant from the bottle when the engine cools.

"Air locks" in the cooling system are essentially impossible with these trucks. Other vehicles may need specialized bleeding or filling procedures, but not these trucks.

As long as ive had the truck its never overheated, went above normal temp once but luckily i was pulling into the driveway so i was able to shut it right down. That was last summer

How old is this radiator? Has it ever been professionally cleaned, or replaced?