FYI, Do not drain the hot coolant from a hot engine.

WolverineFW · **Posted:** Thu Jul 16, 2020 12:02 pm

layback40 wrote:

Its great to hear that you have some good understanding of the practicalities of heat transfer FW.
The air entering the engine has ample contact with coolant etc to warm before it hits the liner. The air has a very low heat capacity compared with the coolant, The heat transfer coefficient between the liner & the air is very low compared with that of for the coolant & the liner & conduction within the metal in the engine. In simple terms, that is why a liquid/liquid heat exchanger has a much smaller contact area than an air cooled one of the same duty. There would be a lot of water (coolant) vapor present that would be able to condense to keep the temperature up.
What is being suggested is a bit like saying that if metal like a liner at 212f is exposed to normal air temperature it could crack.
My thoughts are in this case are that the liner in question was already cracked.

Agree with this in terms of the heat transfer abilities of air and coolant.

I was thinking of it in the opposite direction.....the liners are hot and the coolant normally dissipates a lot of heat to allow them to cool down. You have just shut down the motor and then quickly drain the coolant. Coolant is replaced with air which due to its low heat capacity now cannot cool the liners sufficiently and they increase in temperature briefly due to lack of heat transfer to the air that has replaced the coolant. Possible this thermal shock caused the liners to fail???

I think the really odd part is the fact that all four liners were apparently cracked. What set of circumstances would lead to all four failing at the same time?

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Jett · **Joined:** Fri Apr 17, 2020 12:07 am **Posts:** 250

Okay since some of you want to prove it right instead of wrong, I’ll concede that there is a chance, and that chance is 1:1,000,000,000 give or take a few hundred million.
The normal designed life of a Cyl liner is much more extreme than a non running coolant drain situation where air is replaced. Air as you may know is an excellent insulator, and this means it will struggle to cool anything hot which is why we use water in the first place to cool our engines. And the operation of the thermostat is to allow and engine to get hot and then when it opens it dumps a big gulp of cold water into the engine where that water immediately cools the Cyl liners by up to 100°. So if anything that is what caused them to crack, not the air. And by the way, an engine that is shut down doesn’t continue to make Or distribute heat longer than a few seconds, With the exception of the hot turbo, so that isn’t going to overheat the liners in the absence of water.

layback40 · **Posted:** Thu Jul 16, 2020 7:54 pm

WolverineFW wrote:

Agree with this in terms of the heat transfer abilities of air and coolant.

I was thinking of it in the opposite direction.....the liners are hot and the coolant normally dissipates a lot of heat to allow them to cool down. You have just shut down the motor and then quickly drain the coolant. Coolant is replaced with air which due to its low heat capacity now cannot cool the liners sufficiently and they increase in temperature briefly due to lack of heat transfer to the air that has replaced the coolant. Possible this thermal shock caused the liners to fail???

I think the really odd part is the fact that all four liners were apparently cracked. What set of circumstances would lead to all four failing at the same time?

Sent from my SM-G965W using Tapatalk

The cooling that occurs when you first turn the engine off is very quick to equalize the engine temperature. By the time you get out of the car & get to the drain plug, most of the block & liners will be within a few degrees of each other. Even if parts of a liner was at say 400f during running, it would be much cooler by the time air was in the system. A hot liner say at 400f doesnt crack when air cooled.
I am very suspicious that we are not being told the full story. Was this a drag car that burst a hose 1/2 way down a 1/4 mile & continued to run to seize?
A burst top hose would empty the coolant much quicker than draining & even then it takes time to seize. Was the engine quickly emptied & then filled with cold water?

turblediesel · **Posted:** Thu Jul 16, 2020 8:26 pm

Where were the cracks?

There's bound to be heat transfer between the aluminum head and the cast iron block. Sleeves are in contact top and bottom. A big differential between them might cause thermal stress.

Consider moving a warm cast iron frying pan barehanded into the sink and running hot, warm, or cool water into it. The handle becomes too hot to manage bare-handed. Cold water into a hot frying pan can crack it.

Jett · **Joined:** Fri Apr 17, 2020 12:07 am **Posts:** 250

layback40 wrote:

WolverineFW wrote:

Agree with this in terms of the heat transfer abilities of air and coolant.

I was thinking of it in the opposite direction.....the liners are hot and the coolant normally dissipates a lot of heat to allow them to cool down. You have just shut down the motor and then quickly drain the coolant. Coolant is replaced with air which due to its low heat capacity now cannot cool the liners sufficiently and they increase in temperature briefly due to lack of heat transfer to the air that has replaced the coolant. Possible this thermal shock caused the liners to fail???

I think the really odd part is the fact that all four liners were apparently cracked. What set of circumstances would lead to all four failing at the same time?

Sent from my SM-G965W using Tapatalk

The cooling that occurs when you first turn the engine off is very quick to equalize the engine temperature. By the time you get out of the car & get to the drain plug, most of the block & liners will be within a few degrees of each other. Even if parts of a liner was at say 400f during running, it would be much cooler by the time air was in the system. A hot liner say at 400f doesnt crack when air cooled.
I am very suspicious that we are not being told the full story. Was this a drag car that burst a hose 1/2 way down a 1/4 mile & continued to run to seize?
A burst top hose would empty the coolant much quicker than draining & even then it takes time to seize. Was the engine quickly emptied & then filled with cold water?

Yes. You explained it better. Also, while I don’t have a PhD or metallurgy degrees, I am a career welder and I’ve seen a lot of cracked metal, cracked from heat, cooling, and been around some hot metal and I’m observant to those things. So that is something and you’re right it’s just my opinion, but it’s correct lol.

rankom · **Posted:** Fri Jul 17, 2020 9:38 pm

well I remember back in the 80s as a young apprentice in the winter months they wouldn't let us change oil when the engine is hot. They must have had some reasons why.

Jett · **Joined:** Fri Apr 17, 2020 12:07 am **Posts:** 250

rankom wrote:

well I remember back in the 80s as a young apprentice in the winter months they wouldn't let us change oil when the engine is hot. They must have had some reasons why.

If you want to keep elephants out of your yard what you do is put jugs filled with milk on all 4 corners of your property. It works! I’ve been doing it for years and I have YET to find a single elephant on my property!

turblediesel · **Posted:** Mon Jul 20, 2020 4:37 pm

Jett wrote:

rankom wrote:

well I remember back in the 80s as a young apprentice in the winter months they wouldn't let us change oil when the engine is hot. They must have had some reasons why.

If you want to keep elephants out of your yard what you do is put jugs filled with milk on all 4 corners of your property. It works! I’ve been doing it for years and I have YET to find a single elephant on my property!

The blue light on your dash will cause oncoming traffic to appear.

FYI, Do not drain the hot coolant from a hot engine.

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