Milky oil in Starboard engine - 2 454's (mercruisers) v-drives. Closed cooling with oil cooler

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I just changed my two over the winter as preventive maintenance ( MerCruiser said ten years ).
Before I bought them from Mr. Cool did some research and they came up with good reviews.
 
I ordered a replacement from Mr. cool very organized and part looks from the pictures to be high-quality
 
Installed the new one. Hopefully this was the source. I ran a test on suspected bad cooler by pressurizing with 100PSI compressed air. Not sure if this is an accurate test or not but no major bubbles as I thought
IMG_2493.JPG
 
Beech2000 said:
I'm headed down to lake today. I have a radiator pump. Told by several people the oil coolers are notorious for water in oil. I'll be purchasing replacements this week. Thanks all
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Did you have a chance to pressure test the cooling system and send the oil in for analysis?

As I mentioned earlier, problems like this can have you chasing your tail based on other people's experience. The only way to solve it is to find out what is wrong. Once you figure out if that is water or coolant in the oil....it will set you on the right path.

The oil/antifreeze picture I posted is from a similar problem where the owner had replaced his intake manifolds 5 years ago with aluminum Edelbrock manifolds. Pulling an oil sample and letting it set for a few days usually tells you what is going on.

In his case, the Starboard motor was consuming antifreeze/oil muddy and his Port was normal. Putting a pressure tester on the cooling system and taking it to 14 psi of showed the Starboard engine was leaking out of the closed cooling system. Again the Port was normal and held 14 psi for 5 minutes. The Starboard dropped to 5 psi in the same time. At this point with coolant in the oil it either was a gasket (intake or head) or a cracked block/head.

With that we checked the intake manifold bolts (easiest thing first) and they had loosened. This leaked coolant from the gasket where the intake meets the head into the oil galley causing the problem. Tightening the bolts and changing the oil a few times solved the problem and the system held 14 psi for 5 minutes.

I personally would have replaced the intake gaskets but it was his choice.
 
PlayDate said:
Did you have a chance to pressure test the cooling system and send the oil in for analysis?

As I mentioned earlier, problems like this can have you chasing your tail based on other people's experience. The only way to solve it is to find out what is wrong. Once you figure out if that is water or coolant in the oil....it will set you on the right path.

The oil/antifreeze picture I posted is from a similar problem where the owner had replaced his intake manifolds 5 years ago with aluminum Edelbrock manifolds. Pulling an oil sample and letting it set for a few days usually tells you what is going on.

In his case, the Starboard motor was consuming antifreeze/oil muddy and his Port was normal. Putting a pressure tester on the cooling system and taking it to 14 psi of showed the Starboard engine was leaking out of the closed cooling system. Again the Port was normal and held 14 psi for 5 minutes. The Starboard dropped to 5 psi in the same time. At this point with coolant in the oil it either was a gasket (intake or head) or a cracked block/head.

With that we checked the intake manifold bolts (easiest thing first) and they had loosened. This leaked coolant from the gasket where the intake meets the head into the oil galley causing the problem. Tightening the bolts and changing the oil a few times solved the problem and the system held 14 psi for 5 minutes.

I personally would have replaced the intake gaskets but it was his choice.
Click to expand...

Well its been 4 months and 51 hours of operation since oil cooler change out. I am happy to report starboard engine is fixed.
Oil is no longer milky and appears normal. Strange as my pressure test of oil cooler showed no leakage. Since I'm changing the oil this week, I'll send a sample out to lab just to make sure. BTW Bolts were all tight on intake manifold and borescope of oil gallery looked oil stained and dark everywhere. Love it and thanks!
 
logical answer and fix. Seeing you weren't losing antifreeze. The cooler was the only place that could put water in your oil.
 
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