Breather vent tube

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SteveP
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Breather vent tube

Post by SteveP » Tue Dec 24, 2019 11:06 am

Little worried! Breather tube has fairly steady stream of Whitish smoke coming from it. Motor is running great otherwise. Don’t see any smoke coming out of exhaust. Is this normal? I know that they boil condensation from oil when they heat up, but this seems more like smoke than condensation

marshthumper
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Re: Breather vent tube

Post by marshthumper » Tue Dec 24, 2019 12:49 pm

Have you done a compression check and leakdown check? Could it be some blow by or excess case pressure from a valve seat or ring? Would also help to have a lil more info. As to what motor you’re running and mods or setup.
Homebuilt 12ft deckover with Lycoming O-360

SteveP
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Re: Breather vent tube

Post by SteveP » Tue Dec 24, 2019 4:21 pm

Sorry I’m new to aircraft engines and far from a mechanic. It’s a 4 cylinder lycoming, I believe to be a 0-290. No I haven’t done a leak down test or a compression test. The motor sat for 5 years or so, I changed oil and it’s been running beautiful other than the smoke. Smoke doesn’t seem to start till it warms up a bit. I was thinking the same thing that it could be blow by, I read somewhere that it would turn the oil black quite quickly if this is the problem and oil would smell like gas. I’ve been keeping an eye on it and it still looks relatively new and doesn’t smell of gas. Not sure if this is the case but could very well be. Plugs are staying clean! Not sure if this helps any.

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Slidin Gator
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Re: Breather vent tube

Post by Slidin Gator » Tue Dec 24, 2019 9:29 pm

If it’s vapor it disappears real quick. Blow by will make your oil temps hot and will push smoke out the blow by (guess that’s where the name came from). No smoke in exhaust is good, probably not a valve issue.

Unless preserved, 5 years of sitting = corrosion. It could easily be rings or valve issue, but the most likely is corrosion pitting of cylinder. It depends if the cylinders are bare steel or chrome. Any chance there is orange paint on the cylinders?

Since you already ran it, I suggest a heavy dose of Marvel Mystery oil in both the fuel and oil. Did you clean the oil filter screen? If it doesn’t have a spin on filter, add one.

Go beat the hell out of it for a weekend, then change the oil and filters, make sure to clean the filter screen, I think them 290’s have a screen.

Do leakdown and compression before and after. If it improves after all this it’s rings and/or cylinder.

As long as it runs, run it!
I grew up thinking I-10 was the Mason Dixon line.
1986 Airboat Engineering Inc., 14' Marsh Master. Refreshed narrow deck, SV O-540, 72” NGQ. A Bob Stossel original.

SteveP
Southern Airboat Member
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Joined: Sun Dec 01, 2019 6:30 pm

Re: Breather vent tube

Post by SteveP » Tue Dec 24, 2019 10:43 pm

Thanks for the info. I did clean the screen when I changed the oil it was pretty gunked up. I think the guy that owned it previously didn’t know it was there. I actually just checked the screen after about 5 hours of running and it’s as clean as could be. I did see the screw on filter adapter you could buy for these things. There is no orange paint on the cylinders. Good possibility of some pitting from sitting so long. Motor seems like it has lots of pep and doesn’t hesitate a bit on acceleration. I will do some checks and if they’re good I guess I’ll keep on givin er! Thanks for the tips.

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