crank case breather pipe

Thanks Tad. Very similar time to my engine. I was very pleased not to have any leak until seventy hours of time. At first I thought perhaps I over filled the oil sump. But now it is leaking a little after each flight. Its really not a big problem but as I was exploring the reasons for blow by in addition to piston ring wear I saw references to the position of the blow by pipe and that if it is in the wrong position that a negative pressure could help suck oil out the pipe so I thought this was worth exploring. Other contributory issues are a bad oil cap seal or a worn front crank seal that lets air ram into the crank case when flying and adds pressure inside the case that results in blow by.

I have not checked the routing on my C90, but I have been led to believe that a little dripping from the breather tube is normal. I also had a top overhaul recently - around 60 hours ago, and got a little drip after break-in. I got the same kind of drip on a car built before the smog recirculation devices were mandated, so it may be just a "feature" of the old design of our engines. If you are in a hangar, you might consider a pan with kitty litter. That way you can keep it clean, but also keep an eye on the quantity of drip. Good luck.

Last year work was completed on the engine of my 415C, including new cylinder heads and new push rod tubes. During the first 70 hours the engine has not leaked a drop of oil until recently. After flying I am now getting a small amount of drips from the crank case breather pipe. On my C85 engine the breather pipe comes over the top of the cylinders, down the back of the engine and ends just above the bottom of the lower cowl close to the cowl opening. I've research possible causes of breather pipe oil leaks and there are several, but the one I am seeking direction on is what is "the proper location" of the breather tube? I've read that if the tube is in the wrong location a negative pressure can create a sucking action that will draw the oil out. However, I've not been able to find any reference to what is the proper location of the breather tube. I have a friend with a Cessna 150 with the 0-200 engine and I note his breather tube goes straight down the side of the engine and ends near the bottom of the front of the cowl. I am thinking perhaps there is less negative pressure at the front of the engine than the bottom of the rear. Any comments are appreciated.