What Causes Piston Ring Noise?

[StLucille]

Piston ring noise can be caused by: broken piston rings, piston ring leakage, poor sealing between the piston rings and cylinder walls, or piston rings hitting cylinder shoulders. Here are the detailed explanations: 1. Broken piston rings: Conduct a single-cylinder cut-off test. If the noise decreases but does not disappear, and a screwdriver placed on the spark plug or fuel injector produces a "pop, pop" sound, it can be confirmed as broken piston rings. 2. Piston ring leakage noise: When the engine is cold-started, a "bang, bang" sound is heard, and blue smoke is visible at the oil filler port, with the frequency matching the sound. During a cut-off test, if the noise disappears and smoke at the oil filler port reduces or stops, it can be confirmed as piston ring leakage noise in that cylinder. 3. Poor sealing between piston rings and cylinder walls: If noticeable blow-by noise persists after the engine warms up, and a cut-off test still shows significant leakage at the oil filler port, it can be confirmed as poor sealing between the piston rings and cylinder walls. 4. Piston rings hitting cylinder shoulders: Listen with a screwdriver pressed against the spark plug. If a "swish, swish, swish" sound is heard, it indicates broken piston rings. If noticeable vibration is felt, it indicates piston rings hitting cylinder shoulders.