Water in Oil, Oil Cooler Problem Maybe ??

beel61

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Apr 22, 2009
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Hi all, Has anyone ever heard of an oil cooler going bad on a mercruiser allowing water to get into the oil ? I just bought a boat today, 454 mercruiser, the owner said he went to use it last year and it would not turn over. Found that water had gotten into the oil and drained about 17 quarts of water/oil from the engine. He pulled the engine out and had it checked out at a race engine shop, they said it looked like new inside, they put it on a test stand, runs great, holds pressure in the cooling system. They seem to think that the oil cooler cracked inside. It looks like a tube that water, engine oil, and power steering lines run through, presumably to cool the oil and ps fluid. Anyone think that is likely ? The owner seems to be a great guy, I believe him and even told him I would pay the same amount even if he told me the engine was bad, as it would save me the hassle of putting it all back together only to find more problems. Is it neccesary to buy a new cooler, or can I just connect the respective hoses ?
 

Maclin

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Re: Water in Oil, Oil Cooler Problem Maybe ??

The engine oil and power steering fluid is under a lot more pressure than the water in the jacket of the cooler, so even if those lines inside the oil cooler did leak then it just puts oil in the raw water and on out the exhaust. Water would have a hard time getting in those lines thru the small cracks and would just get forced out again once the engine was running.

That much water, man, almost sounds like the engine was open to the elements with the carb off or no cover on the carb.
 

TilliamWe

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Re: Water in Oil, Oil Cooler Problem Maybe ??

Exhaust manifolds are the number 1 through about number 4 reason for water in marine engine. Check them out first.
 

beel61

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Re: Water in Oil, Oil Cooler Problem Maybe ??

The engine oil and power steering fluid is under a lot more pressure than the water in the jacket of the cooler, so even if those lines inside the oil cooler did leak then it just puts oil in the raw water and on out the exhaust. Water would have a hard time getting in those lines thru the small cracks and would just get forced out again once the engine was running..
That is actually what's been bothering me about this, especially with the cooler mounted below the engine, it would have to be a catastrophic failure inside the cooler to pump that much water into the engine. I think I will try and pressure test the cooler.

That much water, man, almost sounds like the engine was open to the elements with the carb off or no cover on the carb.
He said he ran it at home for a bit, then the next morning went to the rive and it wouldn't turn over.
 

beel61

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Apr 22, 2009
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Re: Water in Oil, Oil Cooler Problem Maybe ??

Exhaust manifolds are the number 1 through about number 4 reason for water in marine engine. Check them out first.
I thought about those but didn't think that much water could make it's way into the crankcase, although if it wouldn't turn over, that tells me it was hydrolocked with water in the top of the cylinders also, and I guess maybe it could get past the rings ?? I will take a good look at them and pressure test them somehow.
 

Don S

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Re: Water in Oil, Oil Cooler Problem Maybe ??

I've seen it happen on about half a dozen big blocks.
Failed oil cooler. No one has actually been able to explain how the water gets past the oil and fills up the pan, but I have seen it happen.
Pressure check the cooler. Once you see it's leaking, replace it, do several new oil and filter changes with some diesel fuel added, and see how it acts.
 

TilliamWe

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Re: Water in Oil, Oil Cooler Problem Maybe ??

beel, I thought the same thing about the volume of water he drained. Failed exhaust manifold normally just fill up cylinders and hydrolock engines.

But, if DonS says that somehow those oil coolers do this, then they do. Sounds like you may have pinpointed your culprit.

Just humor me, though... take a good look at the exhaust manifolds/riser/gaskets before you reinstall it all, okay?
 

Maclin

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Re: Water in Oil, Oil Cooler Problem Maybe ??

That is certainly a strange one Don! Wonder if any water gets into the power steering system when it happens?

I can see that if the lines are leaking, and the bilge fills up with water for whatever reason and the boat sits a long while, but still, kind of defies logic based on the location of all the plumbing. Yet, when all other factors are eliminated then that is the only one left. That would make a good case study for a tech or engineering school.
 

Maclin

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Re: Water in Oil, Oil Cooler Problem Maybe ??

...or even a House episode....:D
 

QC

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Re: Water in Oil, Oil Cooler Problem Maybe ??

LOL @ Maclin ^^^^^ :D
 

HT32BSX115

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Re: Water in Oil, Oil Cooler Problem Maybe ??

No one has actually been able to explain how the water gets past the oil and fills up the pan,

Actually I can see how it *could* happen.

My oil cooler is not mounted below the water line, but with a path (hole in the oil-water heat exchanger) into an oil cooler that is mounted below the water line, there would be a slight "head pressure" that would allow water to trickle into the oil system. Given enough time it would fill the oil pan/engine right up to the water line.


It would be less likely with the power steering system (my PS cooler IS below the water line) because most power steering pumps are mounted well above the water line.


You know it's below the water line if the boat is sitting in the water and water flows out when you disconnect the raw water hose from the cooler.


Regards,


Rick
 
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