What is a sign of a failing master cylinder?

A soft or spongy brake pedal is a clear indicator of a failing master cylinder. This condition occurs when there is a leak in the hydraulic system, which can lead to air entering the brake lines. The presence of air reduces the effectiveness of the brake fluid in transmitting pressure, resulting in a pedal that feels less firm and more cushioned than normal. This loss of hydraulic pressure means the brakes may not engage properly, increasing stopping distances and posing a safety risk.

Understanding the symptoms of a failing master cylinder is crucial for vehicle safety and maintenance. In contrast, other options such as increased fuel efficiency, vibrations during braking, or high-pitched noises while braking relate to different components or issues within the vehicle's braking system or drivetrain, rather than directly indicating a problem with the master cylinder itself.