How to Determine Engine Cylinder Scoring?
3 Answers
Engine cylinder scoring can be identified by the following symptoms: abnormal rise in water temperature, reduced oil pressure, smoke from the oil filler port, power decline, cylinder flooding, or oil traces on spark plugs. An idling engine that produces noticeable knocking and air leakage sounds can also indicate severe cylinder scoring. The causes of engine cylinder scoring include: 1. Poor lubrication between the piston and cylinder, improper oil selection; 2. Piston ring breakage and seizure on the piston, or piston pin circlip breakage or detachment; 3. Insufficient clearance between the piston and cylinder; 4. Poor engine cooling, cooling system malfunction.
Last time I had my car repaired, the master mechanic mentioned that engine cylinder scoring is quite serious. Simply put, it means the cylinder walls get scratched by the pistons, and you'll hear obvious metal grinding noises, feeling like the engine is roaring without power. When driving on the highway, acceleration feels sluggish, and the exhaust pipe may emit blue smoke or have a burning engine oil smell. The most accurate detection method is to measure cylinder pressure—if one cylinder's pressure is more than 20% lower than the others, it's almost certainly the issue. Experienced drivers often check the dipstick; if the engine oil has shiny metal flakes mixed in, it's likely cylinder scoring. Never push through this problem—shut off the engine immediately and call a tow truck, or the entire engine could be ruined.
As someone who works with engines every day, there's actually a set procedure for diagnosing cylinder scoring. First, during a cold start, the engine makes a dry grinding noise like 'clack clack.' After the coolant reaches normal temperature, if you floor the accelerator, the tachometer will hesitate and fail to climb smoothly. Using a professional borescope inserted through the spark plug hole, you'll definitely see vertical scratch marks on the cylinder walls. Some new cars come with cylinder pressure sensors—when the check engine light comes on, reading the OBD will show abnormal pressure in specific cylinders. The worst-case scenario is when the cylinder wall is completely scored, allowing coolant to mix with the engine oil, turning it into a milkshake-like substance. In that case, the repair costs can be astronomical.
