It's funny you wrote this when you did. I had a different mechanic take
a look at all my leaking pushrod tubes this week. The main problem is
the seals don't get inserted right. After watching him do it there
really is no excuse. You can see all you need to see with a flashlight
and a mirror. You could clearly see where my seals didn't get seated
properly. It doesn't matter which of the two seals you use, they are
the same. My last mechanic used permatex on the seals. Don't. The new
guy puts vaseline on the edges so they seat properly. He also doesn't
use the special tool for the springs, doesn't like it. After
compressing the spring he uses safety wire to hold them in position.
After tube is in place he snips the safety wire and the spring snaps
into place.

Peter R. wrote:

Sigh Nine hours now on the newly rebuilt Continental IO-520 with
Superior Millennium cylinders, and already the primary fuel pump is going
back to the company for repair or replacement. More importantly, oil is
escaping from the #2 and #5 cylinders' push rod tube seals (at the
Continental case end, for those like me who thought it was a cylinder
issue).

My mechanic told me that, in his experience, Continental is known for
problems with these seals.

Anyone have any experience with leaking push rod tube seals?

Granted all of this is covered under warranty, but after three and a half
months down, I wanted nothing more than to fly the wings off this aircraft
now that the engine replacement work has completed.