REFLECTOR: Piston Crack -- Dye Penetrant Testing

Mon Jun 15 09:34:36 CDT 2015

I'm no A & P mechanic but it appears to be where your camera scraped across the piston residue. The walls still have crosshatch the valves look great. If the scratch / crack wasn't there after the test flight I believe there is no problem. However, a drop of dye penetrate will not foul the oil and a black light will tell the truth.
Mike DawsonN104DD 
      From: Bob Jackson via Reflector <reflector at tvbf.org>
 To: 'Velocity Aircraft Owners and Builders list' <reflector at tvbf.org> 
Cc: 'Bob Jackson' <bobj at computer.org> 
 Sent: Monday, June 15, 2015 7:12 AM
 Subject: REFLECTOR: Piston Crack -- Dye Penetrant Testing

While checking the valves (with my new eBay Dental camera 'borescope'), I happened to rotate it 180 degrees and noticed what appeared to be a crack in the top of the #3 piston.  The valves looked great, but a piston crack is scary.  The engine only has 75 hours on it and has not been abused operationally.  The cylinders and pistons were brand new from Continental (for our TNIO-550N).          The lighter gray marks between the crack and piston part # in the photo is where the top of the (plastic) dental camera hit the piston top when I was looking at the valves.  Here's the #3 exhaust and intake valves.      After a few days of head scratching and worry, we used a small wire brush and some AVGAS to clean off the top of the piston along the 'crack' line -- then took it out for an hour long flight (overhead the field at 6000').  I wanted to see if the crack line would re-appear in the exact same spot or not.  But after looking again after the test flight, there was no evidence of any line in the 'after' video -- the top of the piston looked smooth and clean where the stain/crack had been before.  My questions are:·         has anyone seen similar 'crack's or 'oil tracks' on the tops of pistons?·         could it be a splash or 'seep' line of oil or fuel that appears possibly just as the engine is shutting down?·         has anyone ever done dye penetrant testing of pistons before through the spark plug holes?·         would the dye penetrant residuals likely damage anything or contaminate the oil?  We're trying to gather some data and perspective before talking to Continental and the rebuilder and would appreciate your comments or suggestions.  Thanks,Bob JacksonVelocity XL/RG/XCTNIO-550N1000 hrsN2XF
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