This involves the n12 and n16 engine. What causes piston scuffing? Can i still drive with piston scuffing? What are the symptoms of it? Anyone else experience piston scuffing?



video of noise: https://youtube.com/shorts/_U3xvik2HW8?si=SIYxTXURGqjIFYYX


picture:

 

I'm real curious to know what the bore looks like, where that piston came out of.

 

What that video of your exact car with that piston?

 

no, this was from someone else’s car with the exact same noise and symptoms.

 

To answer your question, no you cant have scoured pistons or cylinders.

Time to have mine checked soon

 

Yeah indeed. It looks like that scoring is through the teflon coating and into the base metal. Makes me think the cylinder wall also has vertical scoring. You now run into cylinder egging from piston rock in the bore, loss of compression, excessive blowby, all very bad things that will only get worse and probably quickly.

OP, if you think your own pistons are slapping around in that direction on the piston, really the only way to (A) find out, and (B) fix it, is to get the pistons out. Then you need to take some careful measurements of the bore and piston, bare minimum of telescoping gauges and micrometers (and more importantly the professional competency to use them correctly. I say this because, if you take the cylinder head off a cold engine, you'll probably notice that with a piston at TDC that you can rock the piston in the bore in the axis of bumper to bumper, and conclude it is junk. But that's not necessarily true. The pistons will expand very quickly as the engine runs and take up some of that gap, also, they do need a certain amount of clearance. It's all very carefully engineered (or at least we hope so). Compare measurements of pistons and cylinder with BMW TIS datasheets for measurement tolerance, and make a decision if that is the problem. Usually at this point block machining and oversize pistons is the way to go, but before doing that you'd want to be sure you fixed the root problem, piston slap or perhaps rod knock or whatever was going on.