What Causes the Sizzling Sound After Starting the Car?

[MarleyLynn]

Car starting with a sizzling sound is mainly caused by releasing the brake too slowly during startup. This is a normal phenomenon. When releasing the brake pedal during startup, the engine already has sufficient power to drive the car forward, but the brake pedal has not been fully released. As a result, the moving wheels are restrained by the brake system, producing a sizzling noise. If the car hasn't been driven for a while, the engine oil will flow back to the oil pan, meaning the top of the engine, specifically the valve chamber, will have less oil. Due to the lack of oil sealing and lubrication for the valves, a sizzling sound can be heard from under the car upon startup. This situation is also normal.

[LePaul]

A buzzing sound after starting the car is a fairly common annoyance. I've encountered this situation several times and found that the most frequent cause may be a loose or aged alternator or air conditioning belt. When the belt rotates at high speed during startup, friction against bearings or pulleys can produce a continuous buzzing sound. Once, I opened the hood to inspect and used a screwdriver to gently press on the belt, making the sound location more obvious, which confirmed it was an alternator belt issue. If ignored, the belt may wear out more severely or even break, causing the alternator to stop generating electricity and leaving the car stranded midway. I recommend first driving the car to a quiet place and starting it to listen whether the abnormal sound comes from the left or right side—belts are generally located at the front of the engine. You can check for cracks or slack in the belt yourself, but it's best to have a mechanic inspect it at a repair shop. Adjusting the tension or replacing the belt may be necessary, which isn't costly but is important for safety. Regularly checking the belt's condition during maintenance can prevent this problem from occurring.

[EthanAnn]

A buzzing sound after starting the car is mostly caused by friction in mechanical components, such as the generator bearing or power steering pump. When the bearing wears out and the gap increases, metal friction produces a buzzing noise during operation, while the power steering pump makes noise during cold starts due to uneven pressure. From my experience, if the sound changes with RPM, it usually confirms the issue. Don’t ignore it—otherwise, the bearing may seize, causing the generator to burn out and the car’s electrical system to fail. During inspection, turn off the engine when it’s warm and listen for the sound location in the engine bay; the generator is usually on the right. A simple method is to use a screwdriver or rod to touch components and listen for vibrations to pinpoint the source. If it’s a bearing issue, replace it promptly—costing around a few hundred bucks. Avoid slamming the throttle during daily driving to extend component lifespan.

[JaxonLee]

When you hear a buzzing sound after starting the car, don't panic. Common causes include issues with the belt system or abnormal noise from the air conditioning compressor starting up. The air conditioning may produce a friction sound when operating under high load, especially after turning on the cooling in summer. It's not difficult to check: start the car and turn off the air conditioning to see if the sound disappears. If it does, it might be due to loose compressor bearings. Aging belts can also cause noise; press the belt by hand to check its tension. If the buzzing sound is left untreated, it could lead to component damage and increased repair costs over time. It's recommended to drive to a professional shop to locate the source of the abnormal noise.