What Causes Abnormal Noise When Starting the Car?
3 Answers
Abnormal noise when starting the car may be caused by friction between the brake pads and brake discs, which is a normal phenomenon. Here are some related details: 1. The car's braking system consists of the brake master cylinder, vacuum booster pump, brake slave cylinder, brake pads, and brake discs. When the brake pedal is pressed, the brake pads clamp onto the brake discs, converting kinetic energy into heat to slow down the car. The vacuum booster pump provides assistance when the brake pedal is pressed, helping the driver to apply the brakes more easily. 2. After opening the engine hood, you can see a black metal disc located below the windshield on the driver's side—this is the vacuum booster pump. In front of the vacuum booster pump is the brake master cylinder, which has a reservoir for brake fluid. The brake slave cylinder, commonly referred to as the brake caliper, contains pistons inside. Brake fluid is a liquid that easily absorbs water. If the brake fluid absorbs water, it can lead to reduced braking force and longer stopping distances.
I've been driving for over a decade, and startup noises really depend on the specific situation. If there's a squeaking sound during cold starts, it's probably due to aging belts or a loose tensioner, especially noticeable in humid weather. A clicking noise when engaging the clutch to start might indicate cracked transmission mount bushings. The most concerning is metallic grinding - that could mean brake pads catching debris or worn suspension ball joints. Last time, my friend's car made a clunking noise with every start, and after thorough inspection, it turned out to be excessive wear in the driveshaft universal joint. Honestly, don't delay with such issues. I recommend taking your car to a repair shop for a proper chassis inspection, and while you're at it, check if the engine guard is deformed and touching the exhaust pipe. Addressing these minor problems early prevents them from becoming major ones - safety always comes first.
Last time my car made a clunking sound when starting, which scared me so much that I immediately went to the repair shop. The mechanic said there could be many reasons for such abnormal noises, and it needs to be diagnosed based on the location. If the sound comes from the front, focus on checking the suspension bushings and lower control arms; if it's from the rear, it's mostly due to aging rear axle bushings. In my case, it turned out to be a lack of grease in the driveshaft's universal joint, and applying some grease fixed the issue. For turbocharged cars, a whistling sound might indicate a turbocharger seal leak. During the rainy season, special attention should be paid to rust on the brake discs, as the friction from rust flakes can also cause a rattling noise when starting. I’ve developed a habit of having the mechanic check the chassis rubber components during every maintenance, since these wear parts typically need replacement every five or six years.
