When the brake pedal is depressed by the driver, the _______ applies hydraulic pressure to the brake system.

• A. Vacuum Booster
• B. Master Cylinder
• C. Caliper
• D. Proportioning Valve

Answer: (B)

When you press the brake pedal, you’re applying mechanical force to push a piston inside the master cylinder. The master cylinder is a sealed chamber filled with brake fluid, so as the piston moves it compresses the fluid and creates hydraulic pressure. That pressure travels through the brake lines to the wheel brakes, where the calipers or wheel cylinders convert it into squeezing action on the brake pads or shoes to slow the vehicle. The vacuum booster helps by reducing the effort needed to push the pedal, using engine vacuum, but it doesn’t generate hydraulic pressure by itself. The caliper uses the hydraulic pressure to clamp, and the proportioning valve only tunes how pressure is distributed between front and rear brakes.