anyone else have very slightly leaky pushrod tube seals?

[RobertE]

I've got an IO360 A3B6 that on both sides of the engine has what appears to be pushrod seals that leak tiny, tiny amounts of oil.  I would guess it's the equivalent of one drop per hour of operation.  It came to my attention when I started getting minor streaks behind the lower edge of the cowling.  The leaks appear to come from the seal between the tube and the head, not between the case and the tube.

 

Anyone else suffer from something similar?  Is this a concern?  My mechanic seems unconcerned.

 

Thanks.

 

 

[mike_elliott]

Robert, the pushrod seals are fairly easy to change and relatively inexpensive. Shims can be added if needed to provide the proper seal seating pressure. Yes, you have to pull the rockers and pushrods, but all in, not to difficult to do by an experienced A$P. IF this is the source of the leak and if it is as small as you say, your mechanic is probably right not being too concerned. If it were mine, I would fix it anyway, however.

You can isolate the leak by completely cleaning the engine and suspect areas first, then spraying some Magnaflux developer on the suspect areas, then ground run the motor fairly hard for about 10 min. If you don't have any Magnaflux, white spray foot powder will also work. It will quickly show where the leak truly is coming from.

[N601RX]

The new seals are silicon and should last a long time.  Sometimes the tension plates crack and release the tension.  Lycoming has also used a couple of different style pushrod tubes on the IO360.  The old ones had welded tabs that the spring plates push against.  I had a couple of mine crack around the weld.  The newer style I replaced them with were one piece stamped. 

[MooneyBob]

Just make sure there is no other reason for the leak. My was leaking too. The reason was stuck exhaust valve and bent pushrod.

[MB65E]

I find rotating the tube in the housing 180° helps spin the seal enough that it reseals. It just puts fresh seating area on the seal.

-Matt

[Zwaustin]

At my pre buy i had my #1 push rod seal leaking. Don Maxwell charged me .2 hours of labor to re seat it. 

[N201MKTurbo]

I usually replace them when they are leaking a lot more than "slightly".