What is a common indication of a failing brake booster?

A common indication of a failing brake booster is increased brake pedal effort. The brake booster assists the driver in applying the brakes by amplifying the force exerted on the brake pedal, primarily through vacuum or hydraulic means. When the brake booster begins to fail, the driver will notice that more physical effort is required to push the brake pedal down, making braking feel more strenuous than usual. This symptom is critical because it can significantly affect the driver's ability to stop the vehicle safely and effectively, especially in emergency situations where quick stopping is necessary.

The other options all relate to issues that may occur within the braking system but are not directly indicative of brake booster failure. For example, an unresponsive brake pedal can suggest issues with the brake hydraulic system or air in the lines, and squeaking noises typically indicate worn brake pads or something similar. Vibrations while braking may point to warped brake rotors or other mechanical issues unrelated to the booster itself. Understanding these distinctions helps in diagnosing brake system concerns accurately.