What Causes the Sound Like Pumping Air When Braking?
2 Answers
Here are two possible reasons for the sound resembling air pumping when braking: 1. Movement of the master cylinder core and booster pump: The sound occurs during the braking process but stops when the pedal is fully depressed and held down. This is likely the sound of the master cylinder core and booster pump moving, which is generally not a major issue, depending on whether the replaced brake fluid meets the required standards. 2. Leakage in the booster: The sound continues when the pedal is fully depressed and held down, indicating a leak in the booster, which requires repair or replacement of the booster assembly. Below is some related information about the braking system: 1. Principle of the braking system: The braking system uses vacuum-assisted braking, and the booster pump produces intake and exhaust sounds during operation. 2. Function of the braking system: The brake pedal, as the name suggests, is the pedal that limits power, i.e., the pedal for the foot brake (service brake), used for deceleration and stopping. The braking system is one of the five major control components in driving, thus it is used very frequently.
I've been driving for over 20 years and have encountered that annoying sound of pumping air when braking several times. This is usually caused by air entering the brake system. Since brakes operate on hydraulic pressure, when air bubbles get trapped in the lines, they compress when you press the pedal, creating that sound. Possible causes include low brake fluid levels allowing air to seep in, minor leaks in the brake lines, or improper bleeding after replacing components like brake pads or hoses, leaving residual air bubbles. If not addressed promptly, air in the system can make the brakes feel spongy and less responsive, increasing stopping distances at high speeds and significantly raising the risk of accidents. My advice is to first check the brake fluid reservoir level yourself—if it's low, top it up with the same type of brake fluid. If that doesn't help, take it to a professional repair shop for a proper brake bleed. Regular maintenance like changing brake fluid every two years and frequently inspecting brake wear can prevent this issue. Always prioritize proper maintenance and safety first.
