REFLECTOR: Piston Crack -- Dye Penetrant Testing

[Ron N VelocityXLFG via Reflector]

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).
>>
>> Cyl-3_Piston_Before-2.jpg
>>
>> Cyl-3_Piston_Before-4.jpg 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.
>>
>> Cyl-3_ExhaustValve-4.jpgCyl-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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