TSIO-360 Rocker Cover Leak

[Pinecone]

Any thoughts. 
 

#6 exhaust rocker cover leaking.  Changed the gasket. Still leaks

Tried another gasket, still leaks. 
Sanded cover flat.  Still leaks.

Chased the threads to make sure bolts go in all the way, still leaks. 

Tried standard and blue silicone gaskets. Still leaks.

Swapped rocker cover with #5, leaks stays at 6. 
 

[Fly Boomer]

19 minutes ago, Pinecone said:

Swapped rocker cover with #5, leaks stays at 6. 

Not actually the rocker cover?  Perhaps something nearby.

[PT20J]

Different engine, but...I had a rocker cover leak on my Lycoming IO-360 and it turned out to have a pin hole in the metal.

[Fly Boomer]

1 hour ago, PT20J said:

Different engine, but...I had a rocker cover leak on my Lycoming IO-360 and it turned out to have a pin hole in the metal.

He swapped covers with a different cylinder, but the leak stayed with original cylinder.

[PT20J]

14 minutes ago, Fly Boomer said:

He swapped covers with a different cylinder, but the leak stayed with original cylinder.

Sorry, missed that. If it's not the cover, and it's not the gasket then it must be the cylinder.

[hubcap]

That annoys the heck out of me. I can’t get mine completely stopped from leaking. I think it must be a Continental thing.

[Pinecone]

A dearth of suggestions. 

[201Mooniac]

1 hour ago, Pinecone said:

A dearth of suggestions. 

You kinda already covered all the normal suggestions.  Can you tell where along the cover edge the leak seems to be coming from?  I presume you made sure the gasket mating surface on the cylinder doesn't show any obvious defects so if it isn't any of the above, and I hate to suggest this, maybe it isn't coming form the rocker cover but somewhere else on the cylinder?

[Pinecone]

The oil is at the bottom of the rocker cover.  

Next step is probably UV dye and a quick run after cleaning.

Where else could it come from?  The pushrod tubes are below (Continental). 

Anyone ever hear of a hole between the bolt hole and someplace with oil?

[Will.iam]

16 hours ago, Pinecone said:

The oil is at the bottom of the rocker cover.  

Next step is probably UV dye and a quick run after cleaning.

Where else could it come from?  The pushrod tubes are below (Continental). 

Anyone ever hear of a hole between the bolt hole and someplace with oil?

Are you running the engine without the cowl? My push rod tube was leaking and the swirling of air deposited oil on the bottom of my rocker cover. Never underestimate oil mist with a swirling wind from the prop. 

[Pinecone]

With out without cowl.  And not a light coat, drops..  Dripping on the turbo

 

[Pinecone]

Thanks to those who helped.

It seems the oil leak is the pushrod tube O-ring.   Today, my mechanic came up to the avionics show with some UV dye and presto, the leak was found.   The oil was running from the pushrod tube junction, down the head and pooling at the bottom of the rocker cover.  Some was creeping up the gasket by osmosis, so it looked like the gasket was seeping