Cracked Water Jackets big block, ???Questions??? Need help!

[jan9898]

Hello, thanks very much for taking the time to read and respond to this.

I'll keep this simple as possible and hopefully give enough detail with this scenario.

1) Raw water cooled big block, Bravo drive.
2) The fresh cool water flow was severely obstructed while the engine was running.
3) The engine overheated severely and remained that way. The engine was left running minutes after the temp. Alarm went off. The temperature gauge shot up so high it passed the highest reading.

4) The obstruction was immediately cleared allowing fresh cool water back into the severely overheated engine.

COULD THIS SCENARIO CAUSE CRACKS IN THE WATER JACKETS OF A MERCRUISER BIG BLOCK?????

 

[jan9898]

Re: Cracked Water Jackets big block, ???Questions??? Need help!

I see 60 people looked at this but no response yet, so I'll simplify the question.

Can introducing a coolant/water into to a severley overheated engine that was not previously getting coolant/water, cause cracks in the water jackets of a Mercruiser Big Block????

 

[Juniinc]

Re: Cracked Water Jackets big block, ???Questions??? Need help!

Yes, it could cause the metal to fracture,,,all depends how fast the water was rushed in.
Hopefully U had some hot water left in the system.

 

[jan9898]

Re: Cracked Water Jackets big block, ???Questions??? Need help!

Hey brother thanks for the response..

I've heard many time that this is one of the main ways you can crack a engine..

Thanks for the confirmation!!!

If you don't mind me asking, what is your marine experience or background????

 

[Bart Sr.]

Re: Cracked Water Jackets big block, ???Questions??? Need help!

I am not qualified to answer your question but can offer an FYI that sometimes on a holiday weekend answers come slowly.

Also Welcome to IBoats.

 

[bhammer]

Re: Cracked Water Jackets big block, ???Questions??? Need help!

If you don't mind me asking, what is your marine experience or background????

I see this one comming!!!

Not from an engine standpoint, but from a welding one.. I have expirenced cracking in metal if it is quiched too quick but I think it is rare in the base material and more common in the weld itself. My 2 cents...

 

[Juniinc]

Re: Cracked Water Jackets big block, ???Questions??? Need help!

Porsche mechanic, a long time boater,,,
http://www.renntech.org/forums/index.php?/user/23680-juniinc/

 

[triman]

Re: Cracked Water Jackets big block, ???Questions??? Need help!

Just as an aside, if your car engine boils on a ot day in the summer, how do you get some more water into the radiator?
Down here in the land of Oz, everyone is taught that you carefully take off the radiator cap, stand clear until the geyser is done, then slowly pour water into the radiator WITH THE ENGINE RUNNING, so the cold water mixes with what is left of the hot water and circulates around to allow the engine to come down to operating temperature slowly and reduce the thermal shock.
FYI the BIG marine diesel engines have a limited rev range which may be used during maneouvring, however once clear of a port the engine can be brought up to full sea speed over a period of about 2 to 2.5 hours. Doing the increase slowly minimises the thermal shock on the engine.
So a standard Sulzer RTA56 will have a maneouvring range of, say 45 to 90 RPM, but will do 104RPM at full sea speed.

 

[rodbolt]

Re: Cracked Water Jackets big block, ???Questions??? Need help!

yes its very possible to crack water jackets,typically in the cylinderheads.
with NO cooling water and a hot engine the sudden rush of cold water can lead to thermal shock. cast iron simply doesnt like it much.
however if your not having issues I would be more concerned with a warped head and a blown headgasket.

 

[jan9898]

Re: Cracked Water Jackets big block, ???Questions??? Need help!

First want to say happy Easter to everyone. Let you celebrate with your family in good health.

Rodbolt, Triman, thanks for the response.

 

[JustJason]

Re: Cracked Water Jackets big block, ???Questions??? Need help!

If you take any metal.... steel, aluminum, copper, tin, etc... and get it very hot, and quench it with cold water very quickly, they will all warp, split, crack etc... that's just blacksmithing 101.

 

[zbnutcase]

Re: Cracked Water Jackets big block, ???Questions??? Need help!

So what are your symptoms? Oil in water? Water in cylinder? Have seen that very scenario a few times and by the time the prob is fixed the engine is usually cool enough to take cool water without damage. Usually the cracks I see are 99% freeze damage. 'nutcase

 

[Silvertip]

Re: Cracked Water Jackets big block, ???Questions??? Need help!

At sea level, water boils at 212 degrees F. A presurized cooling system containing a 50/50 mix of water and antifreeze will not boil until about 245 or more. So if your big block was raw water cooled it began boiling at 212. Boiling in a block turns water to steam which creates pockets in the water jacket where there is no water. The result is extreme hot spots in the engine which when combined with an inrush of 180 degree cooler water (assumes the body of water was about 70 degrees) causes metal to warp and "crack". You may want to have the heads magnafluxed after teardown to ensure they are not cracked as well. Guages and indicator lights are intended to be monitored and understood. Continuing to run a hot engine is what killed it. An oil pressure gauge is also a key instrument. Low oil pressure does not mean you need to add oil. The dip stick tells you that. It means the engine is sick and needs attention "now" not next week or next month. Monitoring gauges more closely could have prevented the issue and I suspect the lesson you just learned will have you doing that more regularly in the future.

 

[jan9898]

Re: Cracked Water Jackets big block, ???Questions??? Need help!

Thanks again everyone for the responses!! It is very helpfull.

This is a response I received from a different forum. Let me know what you guys think about this response??

Hello,
I?m a mechanical engineer and have worked on engines for over 23 years. The short answer to your questions is Yes.
Introducing any type of a liquid coolant suddenly into an overheating engine when it previously had little or none can cause severe damage and can cause engine blocks to crack.
I believe with Mercruiser big blocks like most engines, the cooling/water jackets are adjacent to the cylinders and piston which is the highest temperature part of an operating engine and even more so at an overheated stage.
Two items can occur in this chain of events that can cause engine block cracks. First, by ?flash? cooling what probably were red hot steel components of your overheated engine, you can make those steel parts become brittle. Second, creating steam and pressure from doing so can cause those now weakened components to crack; it can also cause severe gasket and other failures. Stress or quench fractures will take the path of least resistance or form at the weakest point. As a piston moves rapidly through a cylinder it creates a somewhat solid structure, more than likely this would not be the weakest point and the fractures would form away from the cylinder and piston.
The pressures created under these circumstances can be very significant. There was a point in time in history when similar pressures were used to power locomotives.
You should have turned the engine off immediately, fixed the coolant flow problem, waited for the engine to completely cool and then start it again.
Good Luck
~ Kim

 

[jan9898]

Re: Cracked Water Jackets big block, ???Questions??? Need help!

What about the rest of this response???