A car equipped with a vacuum assist power brake system reads an abnormal amount of pedal effort to stop the car. What could be the cause?

In a vacuum assist power brake system, the booster works by using engine vacuum to increase the force applied to the brake pedal, making it easier for the driver to stop the vehicle. If the system is experiencing an abnormal amount of pedal effort, it indicates that there is insufficient assistance from the booster.

A plugged booster air breather would restrict the airflow necessary for the proper operation of the vacuum booster. This restriction can lead to a loss of pneumatic assistance, meaning that the driver must exert much more force on the brake pedal to achieve the same braking effect. The inability to draw in air can prevent the system from creating the necessary vacuum, ultimately resulting in increased pedal effort when trying to stop the vehicle.

While other components like a damaged brake line, worn brake pads, or a faulty master cylinder can cause issues in the braking system, they do not specifically result in increased pedal effort linked to a vacuum assist system in the same way as a plugged breather. Problems related to those components usually present with different symptoms, such as leaking brake fluid or reduced braking response, rather than an increase in required pedal force due to a lack of vacuum assistance.