Red Seal Automotive Service Technician Practice Exam

How does a vacuum brake booster function to improve braking power?

1. It enhances the brake fluid's viscosity

2. It uses engine vacuum to multiply the force on the brake pedal

3. It employs hydraulic pressure from the brake lines

4. It replaces the need for power brakes

The correct answer is: It uses engine vacuum to multiply the force on the brake pedal

The function of a vacuum brake booster is centered on using engine vacuum to significantly amplify the force applied to the brake pedal. This mechanism operates on the principle of creating a pressure differential. When the driver presses the brake pedal, the diaphragm within the brake booster is actuated, resulting in a difference in vacuum pressure between the two sides of the diaphragm. The higher vacuum on one side essentially creates a greater force that is then transmitted to the master cylinder. This means that much less effort from the driver is required to achieve the same braking power, facilitating smoother and more effective braking, especially in vehicles where substantial stopping power is necessary. Utilizing engine vacuum allows for effective and responsive braking without a power source other than the engine itself, which is why many vehicles incorporate this system. In contrast, other options listed do not accurately describe the operation of a vacuum brake booster. For example, enhancing the viscosity of brake fluid or employing hydraulic pressure from the brake lines does not pertain to the function of the booster, and replacing power brakes suggests a misunderstanding of how braking assistance systems work, as vacuum boosters are typically a component of a power brake system, not an alternative to it.