📌 What is a Brake Master Cylinder and what is its function? In cars, the master cylinder is a control device that converts force (commonly from a driver's foot) into hydraulic pressure. This device controls slave cylinders located at the other end of the hydraulic brake system and/or the hydraulic clutch system. 📌 Here's how a brake master cylinder works: 1. When the brake pedal is not pressed: The cylinder is at rest, the valve is closed, and brake fluid is prevented from contacting the cylin