Oil overboard

What have people done to reduce the amount of oil that comes out the breather? After 145 hours on our IO-360 I'm still getting a significant amount out the breather and on the belly. Originally I used the 90deg hose from Van's to connect the breater port on the accessory case to the firewall mounted aluminum tube, which terminates over the left exhaust pipe (3rd pic). Since then I installed longer, flexible heater hose (1st & 2nd pic) to reroute it higher in the engine compartment (more vertical component) and lowered the oil pressure, which I didn't think would matter but needed to be done anyway (was close to 90psi, now 70-80 psi). I keep 5-6 quarts in the sump, anything over goes out immediately, and fly anywhere from 7-10 hours before having to adding a quart.

Any suggestions? HELP!

It's possible that the crank case is being pressurized by a leaky front seal.
It's more likely that the end of the breather tube needs to be repositioned. LPM had a good article on that a year or so ago. Some locations actually can create a suction that pulls oil vapor out of the tube.
I have used air/oil separators with some success, some cheap and some expensive, but it seems to depend on the installation, so trial and error is usually required for the best results. My best advice on a/o separators is ask around and see what has worked for others. There have been some posts on that in this forum, so you could try a search.

Be careful with using heater hose for oil-it's not designed to carry petroleum and may swell and soften over time. I'd suggest fuel/oil hose-truck parts stores carry the larger sizes. Greg RV9A N4603X (res) (EFI)0-320-H2AD

Sounds about normal to me...

n250jg said:

I keep 5-6 quarts in the sump, anything over goes out immediately, and fly anywhere from 7-10 hours before having to adding a quart.

Click to expand...

Nothing out of the ordinary about that.

I'm running 5.5 to 6.5 qts and adding a qt every 7.5 hrs.

New cylinders will always do much better.

Roger Ping
RV-9
O-320 160 hp

Update

Thanks for the responses guys. I did change how the tube terminates after your suggestion sf3543. Instead of the cut in the tube parallel to the exhaust like in the picture I cut it vertically so the air exiting the cowl would act more like ram air (although I doubt much) than suction when flowing past the tube. Yesterday we did a 1.6 hr x/c and unfortunately this didn't help. BTW, where can I find that LPM article you mentioned? This still could be a low pressure area so I'd like to read up on that.

Greg, thanks for the fuel/oil hose tip. I'll locate some before the annual next month and change it out.

Roger, I have new cylinders, but that's what is worrying me now. After the first engine start we had an induction leak that I couldn't locate until the engine had 0.5 hours, so I'm worried that I glazed the cylinders enough for the blowby to be causing the crankcase to be pressurized. It was going through a quart of oil every 5 hours or less for the first 35, but it instantly slowed down at that point so I thought I was in the clear. I'm thinking of having them re-honed and break them in again, but before going to that extreme does anyone know how else to check for blowby?

Thanks again for the help.

Crank Case Pressure

Per Lycoming tech rep... You can hook up an airspeed indicator to where the oil dip stick screws in. Run the engine and if you have over 80mph (approx 3" water) that is questionable. 100 mph (approx 4" water) is definately high crank case pressure.

I wouldn't think .5 hours with an induction leak would have done any damage.

If you are getting 7 or more hours to a qt of oil I don't see any problems. Some times (okay, not always) with new cylinders you can get 25hrs.

Go fly, have fun and just keep track of your oil consumtion, as usual.


Roger