Yanmar 3GM30F - Contaminated Oil - either water or ?

[peteatbeach]

Fighting numerous issues with one of our Yanmar 3GM30Fs.
- Started with broken gear cover assy on the starter. Replaced at sea and broke the spare. Bad day...
- In port 10 days later drained a lot of water out of exhaust hose. Got the engine started (opened compression levers, bled injectors, etc.)
- Next day running the engine for warm up and oil pressure alarm comes on.
- Checked oil - it is grey in color, not brown.
- Antifreeze level in heat exhanger appears unchanged, maybe 1/2 inch lower, so not sure where contamination is coming from.
- Changed oil and filters 3 times to clear grey oil. Engine starts and runs fine...but for how long.

Initial thoughts include:
- What liquid would turn oil grey?
- How much antifreeze would be required to turn oil grey?
- Head gasket leak?
- Cracked or warped head? (Not aware of any overheating in last 500hrs - since we've owned boat).
- How could seawater get into oil?

Plan to pressure test cooling system soon to see if over-pressure or loosing pressure.

Any other ideas or thoughts?

Thanks

Pete

[Uncle Bob]

Originally Posted by peteatbeach

Fighting numerous issues with one of our Yanmar 3GM30Fs.
- Started with broken gear cover assy on the starter. Replaced at sea and broke the spare. Bad day...
- In port 10 days later drained a lot of water out of exhaust hose. Got the engine started (opened compression levers, bled injectors, etc.)
- Next day running the engine for warm up and oil pressure alarm comes on.
- Checked oil - it is grey in color, not brown.
- Antifreeze level in heat exhanger appears unchanged, maybe 1/2 inch lower, so not sure where contamination is coming from.
- Changed oil and filters 3 times to clear grey oil. Engine starts and runs fine...but for how long.

Initial thoughts include:
- What liquid would turn oil grey?
- How much antifreeze would be required to turn oil grey?
- Head gasket leak?
- Cracked or warped head? (Not aware of any overheating in last 500hrs - since we've owned boat).
- How could seawater get into oil?

Plan to pressure test cooling system soon to see if over-pressure or loosing pressure.

Any other ideas or thoughts?

Thanks

Pete

Water in oil emulsifies and the result is grey.
If you'r lucky the water will have come in through the exhaust, via an open exhaust valve and down past the rings.
Run the engine for an hour or so after the oil changes and see if it reoccurred
If no more grey sludge then all should be well, if sludge reoccurs the I would be looking at the head gasket.
Best of luck.

[roverhi]

On engines that are close to the waterline, water can back syphon through the exhaust from the raw water inlet and get into the engine via the open valves in a cylinder. Probably not much of an issue on a catamaran, however. Can also be forced into the engine via the exhaust from following seas. A working anti-syphon valve or syphon break will cure the first situation and a check valve or manual valve can stop the latter. Other sources can be internal engine failure such as a bad head gasket.

Had it happen a couple of time because of backsyphoning caused by a faulty anti-syphon valve. Did the same change oil change routine as you and the engine ran for 15 more years and two cruises to SoPac. so wouldn't be too concerned about having caused any long term problems with the engine. If it comes back, need to find the source

[a64pilot]

Your right to pressure test though, easy to do and of course pretty much rules out the head gasket.
But unlikely any serious damage has been done if it has run OK for an hour or so, after for or five hours I would no longer worry about it.


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