How to Determine if There is Air in the Brake Fluid?
2 Answers
Methods to determine if there is air in the brake fluid: After starting the vehicle, press the brake pedal. If the first press feels unusually low, but returns to normal after a few presses, and then after releasing the brake pedal for a few minutes, the first press feels unusually low again but normalizes after a few presses, this indicates the presence of air in the brake system lines. A clear sign of air in the system is a soft and ineffective brake feel. Brake fluid is incompressible, while air is compressible. If there is air in the brake system's hydraulic lines, the sensation when pressing the brake pedal will be entirely different, with a noticeable compression and rebound feel. Air in the hydraulic lines can impair the transmission of braking force, weakening the braking power. The method to remove air involves bleeding ports at the end of each wheel's brake line, but this operation is relatively complex and should be performed by a professional repair shop.
Last time I was tinkering with my car, I also encountered spongy brakes. The key is to observe how the brake pedal feels when pressed—if it feels unusually soft, like stepping on cotton, or even goes all the way to the floor; or if you have to pump it a few times to regain some pressure, and the pedal rebounds weakly after releasing, it’s likely due to air in the brake lines. At this point, you might also hear a strange sound underfoot, like a weak spring or a 'whooshing' noise, as if air is leaking. If you notice that the stopping distance is longer than usual while driving, or the ABS kicks in erratically during hard braking, be alert. Don’t delay—take it to a repair shop and have professionals bleed and replace the brake fluid with specialized equipment. Brake issues are nothing to take lightly.
