What are the diagnostic methods for abnormal engine noises?

[Axel]

Diagnostic methods for abnormal engine noises include: 1. If the noise only exists during idle operation and disappears when the speed increases, and there is no significant change in the noise throughout the usage process, it is considered a harmless abnormal noise that can be temporarily tolerated; 2. If the noise appears during sudden acceleration or deceleration, persists when the engine is running at medium or high speeds, and causes body vibration, it is an unacceptable abnormal noise that should be immediately identified and resolved; 3. If the noise suddenly appears during operation and is relatively severe, the engine should not continue to run or be tested for diagnosis, but should be shut down immediately for disassembly and inspection.

[MacCora]

With over a decade of experience in auto repair, diagnosing engine noises requires proper techniques. The most reliable method is to carefully listen to the engine upon startup. A metallic knocking sound may indicate loose connecting rod bearings, while a high-pitched squealing noise often suggests belt slippage. Remember to wear gloves and press on components to test—sometimes it's just a loose alternator bracket causing resonance. A ticking noise during cold starts typically points to hydraulic lifter issues, but if it persists when the engine is warm, check the valve clearance. I recommend gradually increasing the RPM from idle to 3000 several times while listening for changes in sound to pinpoint the problem area. Finally, connect an OBD scanner to confirm with trouble codes. If you can't resolve it yourself, it's best to take it to a shop for inspection to prevent minor issues from escalating into major repairs.

[ClaireAnn]

With years of hands-on experience tinkering with cars, I've learned to categorize engine noises by ear. A pinging sound like a hammer striking sheet metal often indicates carbon buildup causing detonation; a dull rumbling may point to worn crankshaft bearings. I use a long screwdriver as a stethoscope - pressing the tip against the cylinder block with my ear against the handle helps pinpoint exactly which cylinder is affected. Checking flywheel bolt tightness with a torque wrench after shutdown also proves effective. I remember one instance when the timing chain rattled loudly, which turned out to be a seized tensioner. When detecting unusual sounds, don't rush to repairs - documenting the noise frequency and operating conditions before visiting the shop saves time and hassle.

[DiWyatt]

Don't panic if you notice unusual engine noises while driving. First, pull over and turn off the engine. After it cools down, check the oil dipstick level—low oil can cause various strange sounds. When restarting, listen carefully: a tapping sound usually indicates valve lifter issues, while a clunking noise might suggest a loose piston pin. Female drivers can try gently shaking the exhaust pipe; a hissing sound from leaking air may indicate cracked welds. Belt-related noises are particularly easy to identify—sprinkle some water on the belt and start the engine; if the noise disappears, that's the culprit. Remember, avoid prolonged diagnosis in enclosed garages due to the danger of carbon monoxide.