Oil Breather Tube Orientation

Sean

Air balance within the cowling should give you a neutral pressure.  The inlet cowl area vs the outlet will determine if you have low pressure at the outlet.  Where you mount the vent line exit is critical and I suspect you perhaps have the line in a low pressure zone which may be pulling oil vapor from the tank.  i have fixed many aircraft for this issue over the years and almost always, other than simple overfull systems, it is just too much low pressure at the vent outlet.  Cooling outlets work best if they have low pressure behind the cooler to draw the air through the fins.  If you mount a vent line there it could be a lot of the problem. 

Perhaps try moving it to another part of the exit air were there is less airflow. I still recommend the notch.

Cheers

Thanks RW,

The "notch" is such an imprecise recommendation.

My T piece variation on the (reducing negative pressure effect)  concept should  work, as well if not better IF the air pressure at top of firewall/under cowl is actually high, relative to where the oil breather exit is located.

😈