What Causes the Squeaking Sound When Braking?
2 Answers
The reasons for the squeaking sound from car brake pads are as follows: 1. Rust on the brake caliper. If the brake fluid is not replaced for a long time, it will deteriorate, and the moisture in the fluid can cause the caliper to rust, leading to friction and abnormal noise. 2. Slow return of the brake master cylinder. Abnormal return of the brake caliper can also cause noise from the brake pads. 3. Break-in period for new cars. The brake pads and discs of a new car are in a brand-new state and still in the break-in period, which may cause some noise. This is a normal phenomenon. 4. Presence of foreign objects between the brake pads and discs. During driving, foreign objects such as sand or stones can get lodged between the brake pads and discs, causing noise when braking. 5. Hard material of the brake pads. Most original brake pads are made of semi-metallic materials, which can easily produce noise when rubbing against the brake discs. 6. Improper installation of the brake system. If the spacing between the brake pads and discs or the tightness of the nuts is not properly adjusted during installation, it can cause noise. 7. Noise when braking in reverse. Brakes primarily work during forward motion, so prolonged wear in one direction can create burrs on the reverse side, causing noise when braking in reverse as the burrs rub against the brake disc.
I've been driving for over a decade, and it's quite common to hear a hissing sound when braking. The most frequent cause is worn-out brake pads being too thin. When the friction material is exhausted, the metal backing plate directly rubs against the brake disc, producing this noise. Another possibility is contaminants in the brake system, such as sand or dust getting stuck in the components, causing abnormal sounds during operation. Additionally, if there's air leakage or bubbles in the brake hydraulic lines, a hissing sound may occur when pressure is applied. I remember my old car had this issue before—after inspection, we found the brake pads were nearly gone, and replacing them promptly solved the problem. I recommend you first visually check the thickness of the brake pads and the condition of the disc surface. If they're below standard or show scratches, visit a repair shop immediately. Also, check the brake fluid level; if it's too low, it might indicate a bigger problem. Ignoring these issues can lead to reduced braking efficiency, longer stopping distances (which is dangerous), or even accidents. Safety comes first—don't delay. It's best to have a comprehensive diagnosis at a reputable repair shop.
