crankcase pressurized through air pressure on bad nose seal is an unusual but possible culprit if you've exhausted other alternatives. I saw that on a neighbor's RV4 with O-320
crankcase pressurized through air pressure on bad nose seal is an unusual but possible culprit if you've exhausted other alternatives. I saw that on a neighbor's RV4 with O-320
The weights in the inverted system that act as valves to switch between oil return and breather functions in the oil separator get dirty and stick. Clean them out with a bit of kerosene.
edit: The NTSB agrees. http://www.ntsb.gov/aviationquery/brief2.aspx?ev_id=20050427X00513&ntsbno=DEN05LA070&akey=1
Service instruction http://myweb.tiscali.co.uk/jbtrellis/PDF_Docs/Lycoming_SI139_ Inverted_Oil _Flush.pdf
What color is the oil?