What Causes the Thud Sound When Starting and Braking a Car?
2 Answers
Reasons for the thud sound when starting and braking a car: 1. If the thud occurs during emergency braking, it may be due to the activation of the ABS anti-lock braking system; 2. If the thud occurs during low-speed braking, it may be caused by issues with the brake pads or brake discs, such as incorrectly installed brake pads, mismatched models, or foreign objects on the brake pads or discs; 3. If the thud occurs when starting, it is likely due to foreign objects in the tire treads; 4. There may be a fault in the car's suspension system; 5. If the abnormal sound occurs during sudden starts and there is no noise when the engine is idling, the issue is likely with the carbon brushes inside the starter motor.
A clunking sound when braking at car startup is actually quite common. My car used to do the same, and it's usually an issue with the brake pads. If the brake pads are worn too thin or have debris stuck in them, they can make a clunking noise from friction during initial movement. Sometimes, it's due to loose ball joints or bushings in the suspension system, causing chassis vibration when braking. Or, with new cars during the break-in period, components may not have settled properly, leading to temporary noises. I typically start by checking if all the wheel bolts are tightened and inspecting the brake disc surface for rust or scratches. If the noise persists or the brakes feel less responsive during startup, I take it straight to the repair shop—they can use professional tools to test brake fluid pressure or caliper condition. Never ignore it; brake safety is critical, as failure mid-drive could be extremely dangerous. For regular maintenance, I periodically clean dirt around the wheels to minimize such noises.
