What Causes Slight Vertical Scratches on Cylinder Walls?
2 Answers
Cylinder walls with slight vertical scratches are typically caused by poor cylinder lubrication or prolonged overload operation. Below are detailed explanations of the causes: Scratches due to poor cylinder lubrication: This condition is generally caused by inadequate cylinder lubrication, such as prolonged cold starts, excessively low engine operating temperatures, absence of a thermostat, incorrect oil viscosity for the application, or extended maintenance intervals. Solution: After repairing such an engine, it's necessary to adjust the oil specifications and usage methods, avoiding prolonged cold-engine driving, among other measures. Scratches due to prolonged overload operation: This condition is also commonly referred to as cylinder offset wear. Such wear indicates that the engine frequently operates under heavy loads for extended periods, resulting in excessive lateral forces on the piston and violent piston reversals. Examples include frequent heavy-load hill climbing, frequent overloading, or frequent lugging (driving in too high a gear). Additionally, engine detonation can cause the piston to endure extra impact forces, even oscillating within the cylinder, leading to excessive wear in a specific direction. Solution: During major overhauls of such engines, it's necessary to replace the crankshaft and connecting rods, precisely bore the cylinders to realign the cylinder axis. Post-repair, adjust usage methods, use gasoline with the appropriate octane rating, and avoid overload operation.
As a seasoned mechanic, I've encountered this issue frequently. Slight vertical scratches on the cylinder walls are most likely caused by severely worn piston rings. Piston rings are responsible for sealing the cylinders and scraping off excess oil; when they age or break, they can scratch the walls during operation, creating straight marks. Another common cause is foreign particles entering the cylinder, such as dust or metal debris from the intake or oil system, which can leave scratches as the piston moves up and down. Insufficient lubrication, increasing friction, can also lead to this problem. I recall a customer's car that was neglected for a long time due to this issue, resulting in a sharp increase in oil consumption, reduced engine compression, and poor performance. These minor scratches shouldn't be taken lightly; they may indicate serious internal engine wear. I recommend regular maintenance as the key: change the oil and air filter on schedule and use high-quality lubricants for prevention. If scratches are already present, have a professional shop inspect the internal condition with a borescope—sometimes, replacing the piston rings can resolve minor issues.
