What Causes the Buzzing Sound in a Car Engine?
3 Answers
Car engine buzzing sound is caused by: 1. The need to replace engine oil or the viscosity of the oil does not match; 2. The oil does not fully lubricate all parts of the engine; 3. Increased gaps due to engine wear; 4. Excessive carbon buildup in the engine, throttle, or spark plugs; 5. A dirty air filter. The engine is the device that provides power to the car, converting the thermal energy of gasoline and diesel into mechanical energy by burning and expanding gas in a sealed cylinder, which pushes the piston to perform work. Its components include: 1. The valve train; 2. The crankshaft and connecting rod mechanism; 3. The ignition system; 4. The cooling system; 5. The lubrication system; 6. The starting system; 7. The fuel supply system.
Last time my car had the same issue, it sounded like a swarm of bees following me while driving. The most common causes are a loose or aged/cracked belt, especially during cold starts when it squeals and vibrates. If the water pump's bearing is worn out, it can also produce a buzzing noise—check the water hose; if it's shaking violently, that's likely the culprit. If the noise appears when the A/C compressor kicks in, chances are the internal bearing is shot. Oh, and don’t overlook the engine mount bushings—when they degrade, the engine directly clashes with the frame. My advice: record a video of the sound for your mechanic to diagnose. Start troubleshooting with the belt tensioner first—these accessory system fixes usually aren’t too expensive.
Low-frequency engine humming is usually caused by out-of-round rotating components. The most typical case I've seen is delamination of the crankshaft pulley rubber layer - it looks intact but wobbles when rotating. Modified cars require special attention to exhaust manifold and chassis component interference; it sounds like humming from a meter away but turns into metallic vibration noise near the exhaust pipe. Recently handled a case where the generator one-way pulley was stuck - the higher the RPM, the denser the noise. The most troublesome issue is turbocharger piping resonance, requiring a stethoscope to slowly locate which clamp is loose. While this sound doesn't affect driving, it particularly wears out bearings, so early treatment is recommended.
