Crankcase Breather Tube

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8209
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Name: Brent Wilson
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Crankcase Breather Tube

Post by 8209 »

I'm new to the sight and the 140. I thought I saw a post on how to control the oil out of the crankcase breather tube instead of just letting it blow out uncontrolled. The c85 hasn't been run in about 10 years so I may just have to live with some oil venting, not sure.
Any suggestions would be great.
Thanks
V529
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Name: Victor G
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Re: Crankcase Breather Tube

Post by V529 »

Several comments.

1. If your aircraft has not been flown or had the engine run in 10 years, chances are there is corrosion inside the cylinder bores and the rings may not be seating very well. In which case you would have excessive crank case pressure and not much you do with the breather tube is going to help.
the "fix" for this would be removing the cylinders, honing them and installing new rings.

2. Assuming you have decent ring sealing (seating), then a few things could be tried.
2A. Get a C-150 Aerobat crank case breather elbow. (the elbow that threads into the right, forward side of the engine case) It has a 2-3 inch tube that sticks into the engine, making it more difficult for oil mist to escape the crankcase while still venting excess pressure.
2B. Run the breather tube over the top of the engine,(over cylinders 3 & 1) then through the aft baffling, then down to the bottom of the cowling, inbetween the engine and the fire wall. (NOTE: if you run your breather "over the top" be certain to insulate the section above the cylinders, as any winter flying could potentially freeze the water inside the tube and block your breather, This is bad and could blow our your front crank seal in flight)

Does this point you in the right direction?
8209
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Joined: Tue May 01, 2018 7:00 am
Name: Brent Wilson
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Re: Crankcase Breather Tube

Post by 8209 »

Yes it does. Thank you
My cylinders are clean and I believe are sealing good. So where would I get this "aerobat elbow"?
Thanks for your reply.
6298
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Name: Randy Thompson
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Re: Crankcase Breather Tube

Post by 6298 »

It is perfectly normal to get an oil drip out of the breather. It is venting the engine and in that vented air is oil vapor. I have tried the aerobat breather mod and removed it after finding that is did the same thing. I bought one 140 that had a metal salt shaker at the end of the breather tube. No drips until it filled up with oil. Removed that, too.
Randy Thompson A&P IA Pilot
Hold STC SA547EA for installation of O-200 engine in Cessna 120/140 and 140A"s
Overhaul small Continentals
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