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- Jan 5, 2018
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O-540 (1900 SMOH) in my Comanche likes to blow oil out the breather at a bothersome rate if I keep the oil above 6qts to the point of the oil streaks on the belly. (yeah, I know, keep it at 6qts but I'm looking for solutions...) Oil doesn't turn black quickly like an issue I had with a prior O-360 but I've started to notice a bit of oil streaking on the top edges of the nose cowl and a fine mist on the windshield after long flights.
I've replaced the oil breather hose and cleaned the aluminum tube checking to make sure the whistle holes were clear. No change in oil blow by.
Checked the prop and spinner, which is a sealed McCauley 3-blade Blackmax. Not leaking there.
Can a leaking front crankcase seal cause a pressurization issue in the case which is forcing my oil out the breather? Maybe a minor case seam leak in the front of the motor? Thoughts on other causes?
I've replaced the oil breather hose and cleaned the aluminum tube checking to make sure the whistle holes were clear. No change in oil blow by.
Checked the prop and spinner, which is a sealed McCauley 3-blade Blackmax. Not leaking there.
Can a leaking front crankcase seal cause a pressurization issue in the case which is forcing my oil out the breather? Maybe a minor case seam leak in the front of the motor? Thoughts on other causes?
