What Are the Common Causes of Piston Slap Noise?
2 Answers
Common causes of piston slap noise: 1. Excessive temperature causing piston deformation, leading to slap noise. 2. Engine detonation causing slap noise (due to damaged knock sensor). 3. Excessive engine ignition advance causing detonation. 4. Excessive clearance between piston and cylinder. 5. Overly tight fit between piston and pin. 6. Overly tight connecting rod with overly loose piston pin. 7. Bent connecting rod causing piston misalignment. Relationship between abnormal noise and temperature: 1. Noise occurs at low temperatures and diminishes or disappears as temperature rises. 2. Noise occurs at high temperatures and diminishes or disappears as temperature drops.
As a seasoned car repair veteran, I must say that piston slap noise is quite common in engines, often caused by excessive wear due to too much clearance between the piston and cylinder. Older engines are particularly prone to this issue - wear widens the gap, making the piston unstable during up-and-down movement, resulting in a metallic clunking sound when accelerating. Another common cause is loose piston pins or excessive connecting rod bearing clearance - these parts tend to develop problems when aged or improperly installed. Sometimes it's caused by cylinder wall wear or deformation, like when running long distances without oil changes, which can make cylinder surfaces uneven. I suggest car owners not ignore such noises - timely inspection can prevent more serious engine damage. Regular oil changes and monitoring coolant temperature are simple preventive measures.
