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

racertracer · **Posted:** Sat Jul 11, 2020 3:54 pm

FYI, Do not drain the hot coolant from a hot engine. You will crack your cylinder sleeves and trash your engine

racertracer · **Posted:** Sat Jul 11, 2020 3:56 pm

Just thought I'd post that little bit of info from personal experience .. circa 2010 era.

flash7210 · **Posted:** Sat Jul 11, 2020 7:05 pm

layback40 · **Posted:** Sat Jul 11, 2020 9:29 pm

I find this interesting.
Always I try & drain the cooling system when hot.
The reason being that when hot, the main contributor to sludge, aluminum hydroxide, is more soluble at higher temperatures. Its the red sludge that blocks radiators. Some cleaning additives also recommend draining while hot.
I cant see how an empty hot engine would have issues. If you introduce cold water into it there could be a problem.
Sleeves can be heated very hot & left to cool in the air without cracking.
In your bad experience, what sort of crack formed & where on the sleeve was it?

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

I find this highly unlikely

racertracer · **Posted:** Mon Jul 13, 2020 10:15 am

Oh yeah, it happened.

racertracer · **Posted:** Mon Jul 13, 2020 10:17 am

Highly unlikely? Don't believe me? Go ahead and try it and report back.

racertracer · **Posted:** Mon Jul 13, 2020 10:28 am

I have pictures... somewhere.... No one believed it could happen then either and neither did I, hence the reason why I went ahead and drained the coolant in the driveway a few minutes after arriving home from a long drive from Advance Auto Parts with two gallons of g05 all ready to flush the coolant. opened the drain cock and within a two minutes of draining the coolant i heard the sound of steel dings, 4 times. I didn't know what it was. oil in coolant showed up while flushing it and i didn't know where it was coming from. Opened the engine a few weeks later and found the cracks on the sleeves. All four of them.

WWDiesel · **Posted:** Mon Jul 13, 2020 1:31 pm

racertracer wrote:

Highly unlikely? Don't believe me? Go ahead and try it and report back.

Wow! In all my years as of a mechanic I don't recall ever hearing of this, you are the first. :shock:

Certainly not saying it could not happen since it happened to you, anything is possible when it comes to rapid metal temperature rate of change.
We were always taught early on many, many, years ago to never pour cold water or antifreeze into a hot engine for much the same reasoning.
I have seen radiators busted due to this!

This is very good information to be aware of what happened in your case, as it is always much better to err on the side of safety, just in case.
It just might save you a whole lot of headaches and a bunch of money. :wink:

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

racertracer wrote:

Highly unlikely? Don't believe me? Go ahead and try it and report back.

Okay I’ll go ahead and take it a step further, that is not possible. Now pouring in cold coolant? That’s another story. But draining hot coolant from a hot engine is not why your head cracked friend, it’s just not.
My suspicion is that you had an air pocket that caused a hot spot after refilling, or maybe it was just coincidence. Your experience of one time does not convince me, sorry. Thanks for sharing, but I think you’re looking in the wrong place.

WolverineFW · **Posted:** Mon Jul 13, 2020 4:41 pm

Jett wrote:

racertracer wrote:

Highly unlikely? Don't believe me? Go ahead and try it and report back.

Okay I’ll go ahead and take it a step further, that is not possible. Now pouring in cold coolant? That’s another story. But draining hot coolant from a hot engine is not why your head cracked friend, it’s just not.
My suspicion is that you had an air pocket that caused a hot spot after refilling, or maybe it was just coincidence. Your experience of one time does not convince me, sorry. Thanks for sharing, but I think you’re looking in the wrong place.

His head did not crack. His cylinders liners cracked....

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layback40 · **Posted:** Mon Jul 13, 2020 6:55 pm

racertracer wrote:

I have pictures... somewhere.... No one believed it could happen then either and neither did I, hence the reason why I went ahead and drained the coolant in the driveway a few minutes after arriving home from a long drive from Advance Auto Parts with two gallons of g05 all ready to flush the coolant. opened the drain cock and within a two minutes of draining the coolant i heard the sound of steel dings, 4 times. I didn't know what it was. oil in coolant showed up while flushing it and i didn't know where it was coming from. Opened the engine a few weeks later and found the cracks on the sleeves. All four of them.

I think the cracking happened when you did the flushing.

PZKW108 · **Joined:** Sun Apr 06, 2014 5:23 pm **Posts:** 461

Jett wrote:

racertracer wrote:

Highly unlikely? Don't believe me? Go ahead and try it and report back.

Okay I’ll go ahead and take it a step further, that is not possible. Now pouring in cold coolant? That’s another story. But draining hot coolant from a hot engine is not why your head cracked friend, it’s just not.
My suspicion is that you had an air pocket that caused a hot spot after refilling, or maybe it was just coincidence. Your experience of one time does not convince me, sorry. Thanks for sharing, but I think you’re looking in the wrong place.

I also don't think it's possible, draining the coolant will not make for a drastic temp change as this engine is a big mass of metal and will cool down slowly.

Now adding room temp coolant to a hot engine can cause damage.... ( I know..)

P.S. I'm not trying trying to discredit OP, but I find that there is a lot of myth and misconception on this forum !

rankom · **Posted:** Tue Jul 14, 2020 10:11 pm

well it is possible, every time I shut down my big truck engine (Detroit 12.7L when hot) it does make that scary clicking sound im guessing its the valve train being very hot. so I agree that draining Coolant when hot is not recommended.

layback40 · **Posted:** Wed Jul 15, 2020 9:19 am

rankom wrote:

well it is possible, every time I shut down my big truck engine (Detroit 12.7L when hot) it does make that scary clicking sound im guessing its the valve train being very hot. so I agree that draining Coolant when hot is not recommended.

Its probably the exhaust manifold & hot side of the turbo cooling down that is making the clicking sound.

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

WolverineFW wrote:

Jett wrote:

racertracer wrote:

Highly unlikely? Don't believe me? Go ahead and try it and report back.

Okay I’ll go ahead and take it a step further, that is not possible. Now pouring in cold coolant? That’s another story. But draining hot coolant from a hot engine is not why your head cracked friend, it’s just not.
My suspicion is that you had an air pocket that caused a hot spot after refilling, or maybe it was just coincidence. Your experience of one time does not convince me, sorry. Thanks for sharing, but I think you’re looking in the wrong place.

His head did not crack. His cylinders liners cracked....

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Lol okay, liners.. did not crack from lack of water inside, impossible.

WolverineFW · **Posted:** Wed Jul 15, 2020 6:17 pm

Jett wrote:

Lol okay, liners.. did not crack from lack of water inside, impossible.

Sure...what ever you say. Mine posting your doctorate in physics for us to vet your qualifications? Otherwise it is just an opinion....and we all know opinions are like arseholes...

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layback40 · **Posted:** Wed Jul 15, 2020 8:15 pm

WolverineFW wrote:

Sure...what ever you say. Mine posting your doctorate in physics for us to vet your qualifications? Otherwise it is just an opinion....and we all know opinions are like arseholes...

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I have a degree in Chemical engineering (1977) & a post grad cert in water management from Vanderbuit(1986).
Was registered as a Chemical Engineer in the state of Texas in the 1980's. Worked for Dow Chemical.
Your turn WolverineFW !

WolverineFW · **Posted:** Wed Jul 15, 2020 8:47 pm

layback40 wrote:

WolverineFW wrote:

Sure...what ever you say. Mine posting your doctorate in physics for us to vet your qualifications? Otherwise it is just an opinion....and we all know opinions are like arseholes...

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I have a degree in Chemical engineering (1977) & a post grad cert in water management from Vanderbuit(1986).
Was registered as a Chemical Engineer in the state of Texas in the 1980's. Worked for Dow Chemical.
Your turn WolverineFW !

Great...at least you are qualified.

I have not stated an opinion either way...but I have not blatantly discounted it either based on conjecture and opinion as have some posters.

Considering a lot of modern diesel engines have wet sleeve liners as illustrated here...

https://www.google.ca/url?sa=t&source=w ... fAUDDvKh6D

....I would not discount the possibility of the immediate evacuation of the coolant could cause a liner failure. What is taking the place of said coolant???? Most likely ambient air, which is going to be cooler and have much less heat absorption capabilities. Relatively cool air replaces hot coolant....I would say it may be plausible.

And I don't have a PhD as I am sure most on here don't have either....but I do work with heat transfer daily as a Refrigeration mechanic. I am not expert....but likely very few on here are either...so the final point is people can type what ever they like on the internet....doesn't make it correct or true in any sense just because they believe it.

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layback40 · **Posted:** Thu Jul 16, 2020 9:01 am

WolverineFW wrote:

Great...at least you are qualified.

I have not stated an opinion either way...but I have not blatantly discounted it either based on conjecture and opinion as have some posters.

Considering a lot of modern diesel engines have wet sleeve liners as illustrated here...

https://www.google.ca/url?sa=t&source=w ... fAUDDvKh6D

....I would not discount the possibility of the immediate evacuation of the coolant could cause a liner failure. What is taking the place of said coolant???? Most likely ambient air, which is going to be cooler and have much less heat absorption capabilities. Relatively cool air replaces hot coolant....I would say it may be plausible.

And I don't have a PhD as I am sure most on here don't have either....but I do work with heat transfer daily as a Refrigeration mechanic. I am not expert....but likely very few on here are either...so the final point is people can type what ever they like on the internet....doesn't make it correct or true in any sense just because they believe it.

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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.

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

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