That's a good point, Paul. I have seen "new" Cessnas with an insulating wrap around the breather tube. I suspect there are two places where that would help prevent ice buildup and subsequent obstruction. One is on top of the engine where a good length of breather tube is in the "cold" side of the engine. The other is near the outlet where the blowby has already cooled and the exposed portion is in the cold airstream. But my speculation is that a pressure drop in the system causes oil to be pushed out of the crankcase through the separator drain line, and for that to happen the restriction (caused by freezing or something else) has to be between the breather vent and
separator. I wonder if it isn't best to just add more simplicity by eliminating the separator and accepting the minor oil loss. Has any OEM included separators with their product? Maybe, but I've never seen one.
Gary
Previously from Paul:
FWIW, I have the Legacy IO-550 and no separator installed. Factory new engine with almost 700 hours. I go through about 1.5QT of oil between 25-30h oil changes (W100). I have a small amount on the belly to clean off and the breather exit is located on the bottom. Compressions are high 70s on all the cylinders.
The breathers on my previous TSIO-520s (Cessna) experienced freezing at FL altitudes and Cessna had drilled a hole at the top of the tube and facing upwards as a safety measure if blockage
occurred. Is there any chance that temperature is playing a role in these incidents?
Paul