Unpleasant surprise while cleaning pistons

[sleepy350]

Hey guys, today in anticipation of picking my head up from the machine shop, I decided to clean 205,000 miles of crud and carbon built up on my piston tops.

Everything looked good, I can even clearly see the original crosshatching on the cylinder walls. Even more surprising I managed to get my GF to help out.


But then I got to cylinder #5.....

Take a look at what I found.




I have no idea what happened here, I don't even remember any marks in the combustion chamber in the head. I'll have to wait till I pick up my head to be sure.

I'm expecting to have to replace the piston. Are there any other things I should look into after finding this kind of damage?

[TurboJake]

You're already on top of the head, so check the cylinder wall really closely.

[FLG]

IMO

If the cylinder wall is fine, knock down the nicks as best you could and it should be fine, looks very minor.

Any idea on the cause?

Sent from my Galaxy Nexus using Tapatalk 2

[Northern]

Could have dropped a valve a while back from whatever reason and a PO or shop could have called it good enough and thrown it back together.

[nomansland92]

Mine has the same on 2 of the pistons and the head but not just as bad. Walls were in great shape also, i would also just fix it the best you can and run it.

[bmwstudent]

IMO

If the cylinder wall is fine, knock down the nicks as best you could and it should be fine, looks very minor.

Any idea on the cause?

Sent from my Galaxy Nexus using Tapatalk 2

exactly

[sleepy350]

IMO

If the cylinder wall is fine, knock down the nicks as best you could and it should be fine, looks very minor.

Any idea on the cause?

Sent from my Galaxy Nexus using Tapatalk 2

No idea of the cause at this point, no debris, no shards, in fact I had no idea the damage was even there until I cleaned up all the carbon. Will look at the head later and look for any signs of damage.

[TobyB]

yummm... ate something. Only real dangers are hotspots causing detonation,
and upper ring land compression causing ring breakage.

Do knock the high spots off... and check the walls again. You're looking
for fine (but deep) scoring that the ring ends leave...

t

[sleepy350]

yummm... ate something. Only real dangers are hotspots causing detonation,
and upper ring land compression causing ring breakage.

Do knock the high spots off... and check the walls again. You're looking
for fine (but deep) scoring that the ring ends leave...

t

Looks like you're right. Look what I found when I picked my head up from the machine shop.