O360 Oil Leak around Exhaust gasket during break-in

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Pilot-To-Be

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So we just got our O360 overhauled, installed and the first 10 hours have been put on it. After the first flight, everything looked perfect except for a slight oil leak around the number 2 exhaust gasket and a little dripping down the exhaust pipe below the gasket. I can wipe it up around the gasket in about 5 seconds, but I’m stumped. My mechanic says it’s oil that’s still getting past the rings as he doesn’t think they’re fully seated yet, but that doesn’t make good sense to me. why only on one cylinder and not the others? Do I need to keep running it at 75% and see if it stops, or is there an issue with the cylinder? The oil consumption is virtually zero, so how much longer do I need to be in break in mode?
 
If it stopped using oil then I would say it is broken it.
My 0 hour rebuilt stopped using oil after 6 hours and now has 700+hrs.
Never any oil out of the exhaust gaskets. You sure? it maybe leaking oil elsewhere and not the exhaust gasket?

I ran mine for 2 hours at 75% power and then 30 minutes at wide open throttle.
Then the second flight was 2 hours 65-75% power and the last 30 minutes wide open throttle.
First flight used a qt of oil, the second flight it used very little oil and by the third flight it stopped using oil. Then I flew it normal.
 
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I found this post about break-in from Lycoming:

Lycoming issued Service Instruction 1427B in 1993 This advises how to break-in an engine following full overhaul, top overhaul etc. As a simple guide, run the engine at 1000 rpm until the oil temperature has either stabilised or reached 140 degrees, do your mag check, then run the engine for 15 minutes between 1000 and 1200 rpm. If all is well, then run your engine at 1500 for 5 minutes. Then cycle your prop. If all is still well, run the engine at full static rpm for no more than 10 seconds. Allow the engine to cool, then shut down. Another leak check and drop your filter. If all is still well, you are ready for the flight test. Preform your runup as normal IAW the flight manual. Normal take off with a shallow climb angle (helps prevent the engine getting too hot) reducing power to climb power settings. Once at cruise altitude, cruise for two hours at 75% power setting. For the second hour, vary the power between 65% and 75%. Following this two hour period, increase power to maximum airframe recommendations for 30 minutes, providing everything is OK. Descend at low cruise power avoiding closed throttle settings (this is most important). After landing, check your fuel and oil consumption and check your oil filters again. If everything is still OK, then continue to operate your aircraft at between 65% and 75% for 50 hours or until your oil consumption stabilises.
 
Pilot-To-Be said:
or is there an issue with the cylinder?
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IMO the leak is a warranty issue and not a break-in issue. I'd talk with the OH shop before further flight. Also document the basics when first noticed leak and what recommendations the shop offers.
 
There might be a casting flaw in the new cylinder's head, if new cylinders were installed. We had a Lyc cylinder leaking oil out from the rocker box that way on the first runup.

The OP might have a leaking rocker cover gasket. Oil can wick along and appear to be coming from somewhere else.
 
Sure it’s not the oil return lines seeping. Oil blows everywhere. Clean engine and recheck. Valve covers?
 
A rocker cover or oil drain back tube would be my first bet. But it should be addressed by a qualified individual, not speculators on the internet.
 
bonefishpete said:
Sure it’s not the oil return lines seeping. Oil blows everywhere. Clean engine and recheck. Valve covers?
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The oil drain tube is on the left side of the head. The exhaust is on the right. Which is why I didn't mention it. Rather far away.
 
Did they use no-blow gaskets? Have the nuts been re-torqed?

I’d change the gaskets on that side and see how it goes. And I’d use no-blows.
 
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