Car Makes a Thud Sound When Starting or Braking?

[StMiranda]

Possible causes for the car making a thud sound when starting or braking are as follows: 1. The fuel cap cannot be opened, or there is a fault in the chassis suspension components, such as lack of lubrication, wear, deformation, etc. 2. Faults in the chassis steering mechanism components, such as tie rods, upper and lower suspension arms, ball joints, etc. 3. Faults in the front or rear wheel bearings, such as wear, lack of lubrication, or burning out. Additional information: Wear on the brake disc can form deep grooves around the disc. Friction between the brake pads and the edges of these grooves can cause abnormal noises. If the grooves are not particularly deep, the issue can be resolved by grinding the edges of the brake pads to avoid contact with the groove edges. If the grooves are very deep, it is recommended to replace the brake disc. It is generally advised to replace the brake disc once for every two brake pad replacements.

[VanEmersyn]

I've been driving for twenty years and have encountered this kind of starting brake clunk several times. The main issue lies with the brake discs and pads, especially after rainy days when the rust on the brake discs acts like glue sticking to the pads, making a clunking sound upon starting, similar to tearing off tape. Another time, the brake caliper was stuck and wouldn't retract when releasing the brake, causing a grinding clunk at the moment of starting. My suggestion is to step on the brake a few times while stationary to remove rust before driving. If the clunking is accompanied by a shaking brake pedal, it's likely that the brake discs are warped and need replacement. Nowadays, I try to avoid using the handbrake when parking, opting instead for the P gear plus bricks to block the tires, which has significantly reduced rust issues.

[ElliotDella]

The repair shop technician tells you that there are three common situations for a clunking sound when starting and braking: The first is severe rust on the edge of the brake disc, which causes noise when the brake pads scrape the rusted area during initial movement. The second is insufficient lubrication of the brake caliper guide pins, leading to poor retraction and resulting in friction noise. The third, which requires caution, is excessive wear of the brake pads, causing the metal backing plate to directly rub against the brake disc. A simple inspection method is to check for metal dust accumulation on the wheel hub—if present, promptly measure the brake pad thickness. For regular maintenance, apply specialized grease to the guide pins monthly, avoiding regular grease as it can corrode the rubber boots.

[VanMariana]

New drivers often encounter this issue, and it startled me too when I first started driving. It's actually the brake pads sticking to the brake discs, especially noticeable if you park immediately after washing the car without drying them. A friend taught me how to handle it: before parking next time, lightly press the brakes and drive slowly for a few minutes to evaporate the moisture; if you already hear a clunking sound, reversing one meter and then moving forward can help. I've been using this method for three months, and now it only happens occasionally after heavy rain, rarely requiring repairs. However, pay special attention to the location of the clunking sound—if it's from the front wheels, it's fine, but if it's frequent from the rear wheels, you should check the electronic parking brake module.

[DiPaislee]

The clunking noise during every start and brake is really annoying, and I've noticed it's particularly obvious in humid weather. Besides rust issues, it could also be due to aging and loosening suspension bushings, causing displacement and collision of chassis components with the brake lines during starts. During the last maintenance, I asked the mechanic to specifically check the control arm bushings, and cracks were found causing slight wobbling of the brake caliper. Fixing it wasn't expensive—just replacing the bushing made it quiet again. For daily prevention, avoid parking in puddles and don't scrape the tires against curbs to reduce impact on the chassis. If the clunking is accompanied by a high-pitched squeaking sound, it might be an issue with the brake pad wear indicator.

[EmiliaAnn]

When the car makes a clunking noise during initial braking upon startup, it's essential to distinguish between cold and warm engine conditions. If the noise occurs when the engine is cold, it's often due to brake pad-disc adhesion and usually disappears after driving a couple of kilometers—no need for concern. However, if the clunking persists during warm starts, the issue becomes more serious. I once experienced a situation where the caliper piston failed to retract, grinding the brake disc until it turned blue. Now, I've developed a maintenance routine: every three months, I check the brake fluid's water content—if it exceeds 4%, replacement is mandatory; I remove the tires to clean brake dust; and I tighten the wheel hub bolts in a diagonal sequence to prevent uneven brake disc wear. Following these maintenance practices has virtually eliminated the clunking issue.