Oil coming from the air filter

[Jim Fitch]

I was cleaning up the engine compartment yesterday and I noticed some engine oil under the drain pan and traced it up to the air filter.  The filter was pretty wet with oil, enough so that some dripped down the side of the engine.  I hate to admit that I haven't checked the air filter for a while but the last time I did I don't remember any oil on it at all.

Everything seems to be running fine.  Does anyone know what might cause this and is it normal or an indication that something is wrong?

Thanks,

Jim
#1103
Sunshine
Scituate, MA

[Craig Illman]

On my M25-XP there's a ventilation hose running back to the air filter from either the valve cover or crankcase vent to capture "blowby". Since I've only had Espresso #1150 since Feb, I don't know what normal is. The foam filter on mine is damp with oil, but not dripping.

Craig Illman

[Ron Hill]

Jim : I'll guess that the vented air from the oil pan is "condensing" into oil droplets.  These droplets accumulate and are probably the culprits that you're looking for.

I wrote an article in the Mainsheet on this topic.  Back in 1989 I took that hose and put it into a 1/3 bottom of a beer can and foam filter.  I collected SO much oil in my apparatus, that I decided there was NO WAY I'd ever vent that hose into the air intake.  After approx. 100 hrs I can squeeze out an ounce or two of oil!!  Still use the same beer can bottom and clean the foam with soap.  

This all started as a way to keep the engine/compartment clean.  Still works 18 seasons later!!  

[John Langford]

I thought the oil in my air filter foam cover was coming from the vent hose but now I am not so sure. I wrapped the end of the hose in paper towel  during my recent three week cruise and never got any oil residue on the paper towel. Nevertheless the air filter foam continues to collect oil and every once in a while eposits a drop or two into the engine sump. The pipe on which the air filter is mounted always seem dry inside so the source of the oil remains a mystery.

[isabel98]

We haven't seemed to get a consensus on this issue. I also noticed considerable oil on my foam filter when changed this week. I understand the concept of "blowby", but doubt that much oil could travel from the vent tube to the air intake without   making a mess of the engine compartment. Unless there is another avenue for the oil to get from the crankcase to the intake, I dont think the vent tube is the culprit. I will go to the boat Sun 6/4 and investigate further and post my findings..

[Stu Jackson]

You could reinvent the wheel, or simply do what Ron did 18 years ago.  Works for us.  We do, however, clean the filter occasionally.

[isabel98]

Upon further investigation, during a 3 hour 2000 rpm test cruise, the new air filter picked up a significant amount of oil that could only have come from the crankcase ventilation tube. I never would have believed that this much oil could basically be sucked out of the air, but it seems to be the only explanation. I will install a catch can at the end of the tube as a way to keep the oil contained and avoid oil intake to engine.. Did anyone purchase a device designed for this purpose? or is fabrication the best route? I'll read the tech notes now that I am a believer...

[isabel98]

Thanks ron, but I cant find your article. What do you mean a "beer can" an actual beer can? and what type of foam did you use, I thought about using a large sponge cut to fit, but I'm not sure what material worked for you. sorry for being obtuse, but can you explain again? thanks in advance..

[Stu Jackson]

August 1990 Tech Notes, either online or on your CD-Rom

BTW, "isabel98" what's your name and hull # and year?

[Ron Hill]

Guys : The amount of oil vapor that come out of the crankcase vent is SURPRISING - a bunch and didn't want to allow all of that oil to be in the engine intake system!!

My "oil catcher" is a simple one which works in the reverse of the air cleaner on your lawn mower.
Make a 4" round piece of foam 6" long.  Then cut a 3/4" hole in the middle of it that goes down 4/5 inches.  Then I took a beer can and cut off the top 2/3s.  I found a eave screen to keep out the leaves - same diameter.  I put the bottom 1/3d of the beer can into the screen with the foam inserted.  Then slide the vent hose into the hole you made.  Find an accessible part of the engine floor to put the oil vent w/hose attached, that you just made.  I put mine in the starboard rear between the engine bed and the soundproofing.  In recent years I've found that if you wrap the outside with a couple of layer of paper towels (held in place with a rubber band) it acts as a "change time indicator".  When the outside of the white paper towels get dark - it's time to clean the "filter" and start again. 

Should have patented it and sold it to you guys for $50 ea, so I could buy a C42!!   

[David Sanner]

Ron, what do you think the long term issue is with oil in the intake overtime?
We're talking a few oz over many hours of operation so wouldn't most of it
just be nearly atomized and just being sucked into the cylinder and burnt?

Or do you think the intake valves might get coated and damage over time?

I like your foam setup but would still like the air that's coming from the crank case
to go somewhere besides the engine compartment/bilge... mainly be sucked up
back into the engine.  Maybe a hose that comes out of a sealed container
(with foam) up to the air filter?

It looks like current 25xpb being sold as new (or factory rebuilt) still just vents
the crankcase next to the intake... one would think if it caused serious issues
they wouldn't do it.

[Ken Juul]

I don't think oil going down the intake is a problem.  I believe the directions are to impregnate the air filter foam with oil before installation to help trap dust and dirt.  Other than dirt blowing off the parking lot at the marina, once away from the dock I think I sail in a pretty dust free environment.  I don't put oil on the intake foam, instead I rotate the foam as the oil saturates it.  When the foam is completely covered I either wash it or replace it and start over.

[Ron Hill]

David : I don't like the volume of oil that I've collected in 25/50 hrs and believe that it might coat and make a sticky intake valve/s.  A little oil might be OK.  I originally did my "beer can mod" back in 1989, as I knew that the engine would would become a dirty mess over time.  Later I talked with Westerbeake and wasn't convinced that their "fix" to the air-cleaner didn't create another problem.  So have stayed with my beer can filter and am still happy with it.  The engine is approaching 5K hrs so something must be right!!

Ken : I don't believe that anyone should "oil" any of their foam NOISE suppressor - even by rotating it !!!  I still recommend that the aluminum alloy shavings in the air cleaner be cleaned with lacquer thinner every spring.  Again, it's the AMOUNT of oil that's collected/ingested in 25/50 hrs!!   Do what you want with your engine.    

Also I had a 1974 LTD Ford SW with a 400ci engine, that in 1973 HAD operated beautifully until the EPA and regs required that the oil pan breather be vented into the carburetor for 1974!! 

[Stu Jackson]

Ya know, we could argue this one until the cows come home, or the ambient air gets into the filter.

Make your choice and go with it, may be that there is more than one way, and not necessarily only one "right" way to do it.

Your boat, your choice, I sometimes say...

[Roger Blake]

My foam filer around the air cleaner has disintegrated...anyone know where in the Chesapeake area (Annapolis, Deale, Alexandria, etc) where I can get another? I think (but am not sure) the Universal # is 301049 (Foam Filter only?).