What to Do When a Car Engine Cylinder is Scored?
3 Answers
Solutions for a scored car engine cylinder: 1. Remove the cylinder head, inspect the scoring on the cylinder wall, and identify the cause of the scoring; 2. If the scoring is minor and caused by the piston fitting too tightly with the cylinder wall, lightly polish the cylinder wall and reinstall the original piston; 3. If the scoring is severe, rebore the cylinder and replace it with an oversized piston, similar to the repair method for a blown engine. Cylinder scoring refers to deep grooves being formed on the inner wall of the cylinder, causing the friction pair between the piston, piston rings, and cylinder wall to lose sealing performance. This results in reduced cylinder compression pressure and loss of power; the leakage of combustible mixture increases the crankcase pressure, which can lead to crankcase explosion in severe cases.
That day while I was driving, the engine noise suddenly became louder with a metallic grinding sound. Upon inspection, it turned out to be cylinder scoring. This is a serious issue—cylinder scoring means the inner walls of the engine cylinders are scratched, usually caused by insufficient or degraded engine oil, or overheating due to cooling system failure. I immediately stopped the car, turned off the engine, and called a tow truck to take it to the repair shop. After disassembling the engine, the mechanic said the scratches were quite deep and only cylinder liner replacement would work, costing nearly 10,000 yuan. Everyone should develop good habits: check the oil dipstick every 1,000 kilometers, use full synthetic oil and change it every 8,000 kilometers; check the coolant more often in summer; avoid prolonged high-RPM driving, especially for older cars which are prone to overheating.
As a veteran mechanic with over a decade of experience, I've handled numerous cylinder scoring incidents. The most common cause is oil starvation, leading to direct dry friction between pistons and cylinders. In such cases, never force the engine to run—shut it off immediately and call for a tow truck. At the shop, we need to disassemble the engine and measure cylinder bore wear. If wear is within 0.15mm, boring can repair it; beyond that requires cylinder liner replacement. After repair, a 500km break-in period is mandatory, though engine performance will remain slightly compromised. I recommend checking oil levels monthly when the engine is cold, inspecting coolant before long trips, and turbocharged vehicles require more frequent premium oil changes—all crucial to prevent oil consumption-related cylinder scoring.
