Universal M18 Crankcase breather with oily mist - SailNet Community
 
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post #1 of 7 Old 07-15-2012 Thread Starter
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Universal M18 Crankcase breather with oily mist

Hey all,

I've noticed that our 1984 sailboat engine and compartment is covered in a film of oil that I suspect is coming from the crankcase breather.

Last year, we routed the air coming out of the breather to the engine air intake (previously there was no tube on the end of the crankcase breather, suspect it was removed by the previous owner).

After our recent vacation that involved a lot of motoring I noticed a build up of oil under the air intake / end of the crankcase breather tube. The oil isn't dripping out of the tube, but holding up a white piece of paper against soon reveals that an oily mist is coming out.

I opened the air intake today and the filter is black with oil and there was a small pool of oil in the bottom of the air filter housing.

The engine (an M18 Universal) has around 2500 hours on it. I suspect the some oil mist would be expected out of the crank case breather, but don't how if thats true or how much would be expected.

Would fitting an oil separator after in the breather tube be advisable? I'm thinking that would at least clean up the air, keep the oil out of the intake and the engine compartment - whilst allowing me to see more directly how much oil is coming of the crank case breather. Not being any kind of expert in these matters there could be reasons why that wouldn't be advisable.

Any advice would be appreciated.
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post #2 of 7 Old 07-15-2012
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Re: Universal M18 Crankcase breather with oily mist

I'm on our third boat with a diesel motor in it. All three have had the crankcase breather tube directed to the air intake in some fashion and some are messier than others.

Ray
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post #3 of 7 Old 07-16-2012
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Make sure all the fittings are good but most important the intake is clean as any restriction will cause blowback from the crankcase.
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post #4 of 7 Old 07-16-2012
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Re: Universal M18 Crankcase breather with oily mist

I don't know how much blow-by into the crankcase is "too much". If a lot of oil is accumulating it may be an indication that it is excessive. If it is plugging up the air filter you might consider moving the hose so that it vents behind the filter. I can't remember how my VW diesel was set up but if I took the oil filler cap off crankcase fumes would blow out but there was never any accumulation that I could see. A compression test may indicate how well the rings are holding up. Perhaps the engine manufacturer could give you some guidance. I have read of cases where excessive blow by casused excessive oil accumulation which resulted in a run away engine. But I would imagine an engine would have to be pretty tired for that to happen.

Paul T
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post #5 of 7 Old 07-16-2012
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Re: Universal M18 Crankcase breather with oily mist

Hey,

How much oil is in the crankcase? Too much (anything above the 'full' mark) can cause that mist. Did you do a lot of motoring with then boat heeled? That can also cause blow back.

Good luck,
Barry

Barry Lenoble
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Mt. Sinai, NY

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post #6 of 7 Old 07-16-2012
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Re: Universal M18 Crankcase breather with oily mist

Same issue: M25XP Air Intake woes

Stu Jackson, C34, 1986, M25 engine, Rocna 10 (22#)
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post #7 of 7 Old 07-16-2012 Thread Starter
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Re: Universal M18 Crankcase breather with oily mist

Thanks all, had a mechanic out of the boat today and asked him about the air breather / filter being covered in oil.

After confirming the amount of oil via the dipstick and looking at them amount of oil around the breather tube, he said it's an older engine and nothing to worry about. Just vent the breather to the bilge with an oil mat beneath it.

I like the idea of a K&N air filter, not sure if I'll have the space, but will look into it.

Thanks all.
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