What Causes the Engine Abnormal Noise to Become Louder?
3 Answers
Engine abnormal noise becoming louder is caused by factors such as rotational speed, load, and temperature. The specific reasons are as follows: Rotational Speed Factors: Excessive clearance between the piston and cylinder wall; piston pin assembly too tight or connecting rod bearing assembly too tight; excessive clearance between the tappet and its guide hole. Load Factors: Piston knocking against the cylinder; loose connecting rod bearings; piston ring leakage; broken piston pin; excessively loose connecting rod bearing cap bolts or melted and detached connecting rod bearing alloy; excessively loose flywheel bolts. Temperature Factors: Excessive clearance between the piston and cylinder wall; piston issues due to incorrect depth and width of the main bearing oil groove; poor lubrication caused by low oil pressure or overheating leading to pre-ignition; opposite directions of the major and minor axes of the piston skirt ellipse; insufficient piston ovality and too small clearance between the piston and cylinder wall; piston deformation; piston ring clearances.
Recently, my car has had this issue too – the sudden increase in engine noise is quite annoying. Having driven older cars before, I know a bit about this. The most common causes are aging or loose belts, like the alternator belt or AC belt, which can squeak after prolonged use. Another possibility is an exhaust leak, especially at joints where rust or cracks can cause a noticeable whooshing sound. Also, if the engine oil is too low or too thin, the friction between internal engine parts can get louder. I remember one time when the noise was particularly bad, and it turned out to be a broken engine mount rubber pad, causing vibration and noise. More serious issues include internal part wear, like problems with the valves or piston rings, which produce a dull sound. It’s best not to delay – get it checked out to identify the exact cause.
When I notice increased engine noise, my first thought is usually low oil level, as insufficient lubrication causes louder friction between parts. If the noise persists after an oil change, belt issues should be considered - aged or loose belts often produce high-pitched squealing. Exhaust system leaks are another common culprit, especially loose exhaust pipe connections. Internal engine component wear like bearing or piston ring clearance also leads to abnormal operational sounds. I've even encountered knocking noises caused by faulty spark plugs before. The key is to properly diagnose the noise source rather than just guessing by ear, and address it promptly to prevent major issues.
