Contaminated Oil

[E. Martinez]

I have a Yanmar YSM12R and am experiencing water contamination in the oil. Have addressed the typical sources such as anti-siphon valve, mixing elbow, and have replaced the head gasket. Have experienced no water lock at start and engine runs normal.Any suggestions?

 

[Henry Weber]

water in oil

It does seem as though you have looked already in the common places. I have a YSB-12 which I overhauled 2 months ago because of similar problems. It was a leaking head gasket. BUT -- when I had the engine all apart I removed the cylinder sleeve and discovered corrosion areas eaten into the sleeve from the back from salt water. In some places the cavity was 80% through the wall. It would not have been much longer before the cylinder would have lost its integrity. Even though you have good compression indicated by normal starting, the fault could be low enough in the bore to not affect compression too much. Just a guess. In any case good luck with the problem.Henry

 

[Mike]

Water in oil

Head gasket most common problem.Incorrect torque, misalignment possible.Hairline fracture in head or block.Very careful inspection should reveal cause of problem. (Remove head again and look for crossover marks of water.Examine both side of head gasketvery closely) Get some really good light in the area to help see properly.