What do scratches and marks on engine cylinder walls mean?
Visible markings or potential scoring seen on cylinder walls through a borescope often create uncertainty about whether the engine has sustained serious damage or cylinder wash from a no-start issue. This leaves owners unsure if the marks are critical or safe to leave alone, or what cleaning steps might be necessary.
What the numbers show
Counted from the threads quoted below. How we count
- The most recent one is from October 2026.
- This comes up 13.8× more often in r/AskMechanics than across the site as a whole.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
Found another way around this?
Share your steps and trade-offs so fellow engineers don't have to reinvent the wheel. No account required.
- 1Spraying brake cleaner through a straw to clean and inspect the surface betterDid this help you?
- 2Consulting online forums or mechanics to verify if the marks are normal manufacturing artifacts.Did this help you?
- 3Honing the cylinder wallsDid this help you?
- 4Tearing down the engine to pull pistonsDid this help you?
- 5Applying chemical treatments to dissolve stainsDid this help you?
- 6Asking experienced mechanics online for their opinionsDid this help you?
- 7dragging a fingernail across the scratch to gauge its depthDid this help you?
- 8honing the cylinder and checking if the diameter is still within specificationDid this help you?
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“accidentally splashed some iron out in my cylinder walls while cleaning some other rusty parts. I can’t feel any texture difference nor catch my finger nail”source ↗
“Okay. Bear in mind I had not established the fact that I fear I may have fuel washed the cylinder bores because my car has had a no-start issue for months and it turns out it's a ground issue, but I was cranking the engine hoping it would fire up but spark is not present. Fuel is involved here, but I thought I might've scored the cylinder walls as a result. So, do you see anything that looks serious? What would happen if I don't clean it with brake cleaner?”source ↗
“Small scratches on cylinder walls. Can i clean this up with a hand honer or should i just get another block”source ↗
“Yup. Its only the 2 middle cylinders.”source ↗
“I got under my 2009 Honda Pilot with 200k miles and noticed there is what looks like spider cracking in the transmission case. I'm not sure what it means, or if it's a ticking time bomb?”source ↗
“I recently inspected the cylinder walls of my 2020 Ford Fiesta ST Mk8 with a borescope and noticed some vertical scoring marks.”source ↗
“I’m not experienced with evaluating cylinder wall wear, so I was wondering whether these marks are considered normal or if they indicate excessive wear.”source ↗