New Cylinder Leaks at Head/Barrel joint?

[GAHorn]

I received an email from one of our “Friends-of-TIC170A” … and will be making a response to him today… But having not ever seen this particular issue, I want to see what our Members have to contribute.

Here’s the basic info in the email:

“ Have you ever seen a fluid leak between the head and barrel of the engine cylinders? Here's what I am dealing with on brand new Superior cylinders for my 0-200. First pic was after overhaul with new Milleniums, about 25 hours. Second pic is with the warranty replacement cylinder from Superior, about 12 hours. All with straight mineral oil, all under 400F CHT, good baffles.

I've had a few IA's suggest that Superior uses some sort of anti-sieze lubricant when assembling the barrel and head and that this stuff is excess and is 'melting' out. There is some doubt that it is engine oil leaking out but it hasn't been ruled out yet. I cannot tell if it is engine oil, it is awfully black but I am burning avgas/mogas so maybe it's a little sootier.

Anyway, here are 2 pics of my issue. ”

Have any of us seen this on New Milleniums?

[Bruce Fenstermacher]

Interesting. I'm assuming compression is good, no leak or low compression mentioned. Then the 'sealant" theory sounds plausible. Should be an easy question to get answered by Superior. It's been 5-6 years since I put Superior cylinders on my 0-300 and didn't have any of this.

[GAHorn]

I am thinking … That since Superior has already warrantied that cylinder suggests it’s an anomaly they consider serious.

Not on an O200 or O300, but on an IO520 and again on an IO470… I have experienced head-to-cylinder failures. The former on a night takeoff about 300’ AGL and was able to land on the remaining runway. (Shook and vibrated so-badly I had a difficult time reading instruments. The smell of gasoline was very convincing. The head blew off completely and ripped the fuel-injection lines loose from the “spider” manifold …so fuel was spraying all-over the operating-at-takeoff-power engine.)

The second during an ordinary compression check performed only 8 flight hours since Annual Inspection when a young mechanic claimed he could hear “hissing” on a cylinder which was testing 70/80.
I couldn’t believe he could hear any “hissing” (the busy airport background noise included numerous operating aircraft and jet takeoffs just outside the hangar)…. so the young-ears-guy sprayed soap-solution onto the cylinder…and sure-enough…it foamed and bubbled energetically right at the head-to-cylinder joint! ..on a cylinder which had JUST passed Annual and still exhibited 70 psi.

[mmcmillan2]

I nearly ripped apart a Lycoming cylinder at the joint. Vibration was tremendous. Large crack found 3/4 around that joint. Rebuilder sent us another to bolt on. I’d suggest grounding plane for now.