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jerry598
05-14-2009, 10:43
Please take a look at the picture below.

There is an slight erosion pit at the 7:00 oclock position on the edge of the #2 piston.

There is a similar pit on the #4 piston as well.

Are these anything to worry about? Near as I can tell, they are about 1/16", or less deep.

Jerry
95 K3500 6.5 turbo, 124k miles
More Power
05-14-2009, 11:32
Are the cylinder walls damaged? Was there a compression loss in those cylinders? Is there a history of glow plug tip failure?

Jim
jerry598
05-14-2009, 11:59
Negative to all. All cylinder walls look good, except for coolant drip stains on the #7 cylinder wall where the head gasket was cracked. I suspect the coolant seeped back into the cylinder when the truck was shut down. The stains are visible and can just barely be felt by hand.

Thanks for the reply.
jerry598
05-14-2009, 12:00
Forgot to say - no compression test was ever done. Dang.
More Power
05-14-2009, 13:41
If the budget supported it, I'd replace the damaged pistons/rings and hone the affected cylinders. This would give you more long-term confidence in the engine. Otherwise, I'd button it back up and run it - after doing a good job replacing the head gaskets. Assuming of course, that the piston defects don't interfere with the piston rings. The top "Keystone" style compression ring runs in a cast iron groove, so what you're seeing likely doesn't reach the ring groove.

I've not seen piston damage like this before. I've seen pistons with holes and thermal cracks, but not one missing a small piece near the outside diameter....

Jim
simon
05-14-2009, 21:45
I had a engine with 6 out of the 8 pistons like that,some on both sides of the square dimple in the piston.all in exactly the same spot as yours. i think it might be the result of cracked precups that have an extremely high localized hotspot acting like a torch ,heat transfer is limited in the precup area between the cracks .As the cracks apear to be right overhead of the burn spots. Maybe worn injectors and high EGT's could be a contributing factor as well.
If you look at the piston edge closely you will see the erosions are realy melted out aluminum.