REFLECTOR: Piston Crack -- Dye Penetrant Testing

[Don Johnston via Reflector]

And engines!

On Mon, Jun 15, 2015 at 11:33 AM, Ron N VelocityXLFG via Reflector <
reflector at tvbf.org> wrote:

>  Care full what you ask for . I hope the lead free gas is compatible with
> our tanks?
>
> Ron
>
> On 6/15/2015 11:16 AM, John Dibble via Reflector wrote:
>
> Looks like lead deposits.  Amazing how fast the lead builds up.  Can't
> wait for the lead-free avgas.
>
> John
>
> On 6/15/2015 9:12 AM, Bob Jackson via Reflector wrote:
>
>  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).
>
>
>
> [image: Cyl-3_Piston_Before-2.jpg]
>
>
>
>   [image: Cyl-3_Piston_Before-4.jpg]  [image: Cyl-3_Piston_Before-5.jpg]
>
>
>
> 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.
>
>
>
> [image: Cyl-3_ExhaustValve-4.jpg]  [image: Cyl-3_ IntakeValve-1.jpg]
>
>
>
> 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 Jackson
>
> Velocity XL/RG/XC
>
> TNIO-550N
>
> 1000 hrs
>
> N2XF
>
>
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