Causes of Abnormal Engine Noises in Cars?
3 Answers
Abnormal engine noises can be caused by several factors including premature fuel injection timing, diesel leakage from injectors, piston impact against cylinder walls, excessive piston ring side clearance, valve stem tip impacting rocker arms, and engine misfire. To determine the specific cause, different noise characteristics should be analyzed as follows: Rough engine operation causes a knocking sound, commonly known as "engine knock". This manifests as loud noises at low speeds, audible from over ten meters away, accompanied by difficult starting. After ignition, the engine runs unevenly with rapid coolant consumption. This noise results from premature fuel injection timing and requires readjustment of the injection advance angle. When engine noises follow certain patterns - alternating between knocking and backfiring, accompanied by unstable RPM and intermittent black smoke emissions - this indicates diesel leakage from injectors. In such cases, injector maintenance is required. A hollow "clunking" sound, particularly noticeable during low-speed operation or sudden RPM changes along with oil burning symptoms, suggests excessive piston-to-cylinder clearance. This increases piston impact against cylinder walls during operation. The solution is to replace either the cylinder liner or piston. A light metallic "clinking" sound audible throughout the cylinder block, resembling a small hammer tapping an anvil (more pronounced during sudden RPM changes), indicates excessive piston ring side clearance. Replace the piston rings, and the piston if necessary. "Clicking" noises around the valve cover (quieter when hot, louder when cold, persisting during low-speed fuel cutoff) primarily result from excessive valve clearance causing valve stem tip to impact rocker arms. Adjust valve clearance to resolve. Intermittent exhaust flow with noticeable tailpipe vibration accompanied by distinct engine noises indicates engine misfire as the cause.
When the engine starts making a clicking noise, I feel it's time to take a closer look. It could be that the belt has aged, and severe wear over time can cause a high-pitched sound; or maybe the engine oil is insufficient, causing dry friction inside the engine and resulting in a clanking noise. Valve issues are also common, where large gaps or sludge buildup can lead to a tapping sound. Another possibility is worn piston rings, causing looseness inside the cylinder and producing a gurgling noise. My old car used to have this problem—it would make strange noises when accelerating, and upon inspection, it turned out the spark plugs were heavily carbon-fouled. This issue shouldn't be ignored; if the engine gets damaged, it could be even more troublesome. I recommend first checking the trouble codes with a diagnostic tool. If you don't have one, try to locate where the noise is coming from. Regularly changing the engine oil and inspecting the belt can prevent most unusual noises. Head to a repair shop as soon as possible—safety first, don't delay.
I've noticed that most engine noises come from internal wear. For example, loose bearings or connecting rods produce dull knocking sounds; insufficient belt tension causes squeaking; clogged fuel injectors lead to ticking due to poor fuel supply; and knocking occurs during sudden acceleration. I often help friends check their cars, and when encountering abnormal noises, I always use a stethoscope to locate the source first—no wild guesses. If it's a chain issue, untimely repairs can lead to chain elongation and engine damage. Low or poor-quality oil is a common culprit, and I've resolved many issues simply by changing to oil with the right viscosity. Abnormal noises aren't always major problems, but they can be warning signs. Pay attention to engine temperature and fuel consumption changes for better judgment. Don't disassemble parts yourself, as it's easy to injure your hands or damage components. It's safer to send the car directly to a professional mechanic.
