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Old 27-12-2014, 08:25   #1
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Join Date: Feb 2007
Location: Live in Boise, boat is in Titusville, FL
Boat: 56' CNSO Mikado Ketch S/V Solace
Posts: 188
oil in fresh water cooling system

Happy Holidays,

I am looking for advice on a problem with my Perkins 6.354 diesel engine.

I recently installed it to replace my Renault 6 cyl. I purchased it from a guy who had purchased it to install in his boat but decided that the project was beyond his capabilities. He sail that it was sold to him as "recently rebuilt"

I had to disassemble it to a long block to get it into my boat and all the machined surfaces looked new and the cylinders had a nice cross hatched hone.

I recently got it running and took the boat out for 6 hours of sea trials. The engine ran great and temp remained around 180F.

After every thing cooled down I checked the fluids. Oil was right on full. When I checked the coolant it was a brown color. I drained it and it appeared to have a oily residue. I filled with clear water and idled up to temp and drained. The water was dirty looking with more oily residue. I decided to clean the system so I added 1/2 box of dishwashing powder with clear water and once again the water was dirty looking. No standing oil but sure seems oily.

I re-torqued the head and checked rocker arm clearance and ran clear water thru again and still dirty brown. I did notice some rusty powder in the bottom of the bucket once all the water evaporated.

My next thought was the oil cooler but quickly realized it was raw water cooled.

The only part on the engine that is not OEM is the exhaust manifold. I purchased a stainless steel unit that is beautifully fabricated from a company in LA.

Any ideas on what the problem could be? The engine runs great and doesn't run hot so I'm hoping that rules out a head gasket.

There does not appear to be any water in the oil sump. The level is still exactly on full. I'll drain the oil next to confirm.

Thanks in advance for your advice.

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Old 27-12-2014, 08:41   #2
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Join Date: Oct 2010
Location: michigan
Boat: CORBIN 39
Posts: 295
Re: oil in fresh water cooling system

If this was my engine, I would not even worry about it unless you got water in the oil. the engine was recently rebuilt you said, that could be just left over crud from the engine block being boiled out just keep an eye on it, check oil often. water in the oil tends to give it a milky appearance.
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Old 27-12-2014, 08:53   #3
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Location: Salem, MA
Boat: Pearson 31
Posts: 535
Re: oil in fresh water cooling system

I had a similar problem with my Yanmar 2GM20F. Slight oil staining in the coolant overflow jug, and when I changed the coolant an oil slick appeared on the surface while refilling. Once the engine was run the oil emulsified in the coolant so it was more difficult to detect. Removed the cooler to clean and discovered thick oil deposits. We did not have any coolant in the crank oil.

It turned out to be the head gasket. From what I remember, the oil pressure is higher than the coolant pressure, so it is possible to have a leak in one direction. Oil to coolant, and not the other way. We did not find any obvious defect with the head gasket once it was removed, so it was probably slowly leaking over a very long time.

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cooling, oil, water

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