Anyone come across this?... I have an 06 F250 SD I bought off the showroom floor in May of '06 with 13 miles on it 😁 it has 90K miles on it I have finally given myself the time to do a complete "BulletProofing" the truck and I mean everything... anyways after I pulled the heads I noticed on the number 5 cylinder what looks like exactly like electricity... on my piston top in two spots... only this piston.... just finished rebuilding and going through the injectors they were all fine but the glow plugs on #3 & #5 both had the heat scoring half an inch higher on the the glowrod than the rest of them...
long story short do I replace the piston or will it be ok with the new glow plugs new glow plug harnesses and injector harnesses?..

 

Looks like it got pushed a little to hard long enough to slightly melt the piston, or injector overspray on a hard pull.

I am sure someone with more experience will chime in.

 

It certainly isn't my area of "expertise", but that was my first thought as well!

 

Spray pattern on that injector is a little "sloppy" -- not sure what caused the streaking, but you can see that the pattern in that spot is short and more concentrated than some of the others
Look and compare with the spray patterns on the other pistons

I don't like to see the spray pattern much outside the piston bowl lip -- the center of the spray jet should hit just inside the lip, so the fuel swirls in the bowl -- that pattern on top of the piston is over spray or a worn hole on the nozzle tip that is misdirecting the fuel

I would suspect that the engine has been a little hot at sometime -- that little mark near the center is a hot spot
Is it a problem ? ...not really
Depends on the tune, and driving habits when towing a load

 

The first question I would have is, were you tuned in any way?

With a stock engine, it's typical to have a minor spray pattern outside of the dish for maybe 1/8 to 1/4". The pattern on this piston is an example of when FSEs would deny a warranty for a blown head gasket. A worn nozzle, as Hydro mentioned, will also cause this.

The lower three spokes show some thermal etching at the tips of the spokes, which resembles the "arcing" you describe, although not the color traces. How much cleaning did you do on those pistons, as it is usual to have them totally covered in carbon?

 

Well I am a general contractor so I am often pulling a trailer or loaded with tools and materials... as far as my driving I come from an Autocross racing family and my friends all claim that I have discovered time travel due to my ability to leave late and show up in time.. hah
As far as the truck it has stock tune, it has an AFE air filter and AFE pickup into the intake and thats it... I am concerned with the piston integrity since after this complete rebuild/upgrade I dont plan on cracking into this engine ever again...

 

Spray pattern is consistent on all the cylinders, as far as the FI is concered and it has got a little hot once or twice. That was just a slight cleaning on the pistons... is the hot spot on the center of the piston equally as worrisome?...

 

Just asked my cousin, works for Mahle with their performance pistons.

Replace it. That is the line they will want to crack on. Not worth the risk