What are the causes of engine knocking sound?
3 Answers
Engine knocking sound is caused by: 1. Bent or twisted deformation of engine connecting rod; 2. Excessive carbon deposits in the engine; 3. Poor engine lubrication conditions; 4. High cylinder pressure at high speed. Solutions for engine knocking sound: 1. If the knocking sound disappears after the car starts and the temperature rises, you can continue driving; 2. If the knocking sound does not disappear after the engine temperature normalizes, the owner should stop and inspect in time to prevent traffic accidents; 3. After removing the cylinder head and extracting the piston, if severe cylinder ovality, scratches, or excessive clearance between piston and cylinder are found, replacement should be performed, including cylinder liner, piston and piston rings; 4. If connecting rod deformation is found, replacement should be prioritized.
I've been driving for many years, and engine knocking sounds are often caused by internal component wear. Broken piston rings or cylinder wall friction, sounding like metal clashing, are mainly due to poor lubrication or insufficient oil, leading to engine overheating. After prolonged high-speed driving, cooling efficiency decreases, causing irregular piston movement and accelerating wear. Excessive carbon buildup can also affect the combustion chamber, creating detonation. If ignored, the noise will intensify, potentially causing connecting rod bending or cylinder block cracks. Once, my car had this issue, and later inspection revealed the need for piston ring replacement and re-breaking-in. Developing a habit of checking oil levels and regularly changing oil filters can effectively prevent such problems. It's best to seek professional diagnosis early to avoid minor faults turning into major losses.
I always think the engine knocking sound is related to fuel, especially when using low-octane gasoline or a lean mixture. Poor-quality gasoline burns unevenly, producing a clicking noise during ignition. Excessive air intake or insufficient fuel supply leads to abnormally high combustion temperatures, causing metal parts to collide and produce noise. Mismatched gasoline grades or clogged fuel injectors are common triggers. This happens more easily in summer due to high temperatures, as poor heat dissipation accelerates abnormal combustion. Switching to high-quality fuel and cleaning the fuel system usually helps. Don’t underestimate this sound—delaying repairs can damage valves and crankshafts. My experience is to check the fuel system every 5,000 kilometers to keep it clean.
