Master cylinders are most commonly found in the clutch and brake systems in cars. In braking system in cars, this component comes into play when the brake pedal is depressed forcing brake fluid to engage the brake calipers and bring the vehicle to a stop. The clutch in many cars also makes use of this component to make the operation of the clutch a lot easier, requiring less mechanical force from the driver. Every master cylinder has a reservoir to supply it with brake fluid so that it can operate efficiently for braking and clutch operation. Most modern cars have this component as a standard feature.
Simply, master cylinder is a device that converts non-hydraulic pressure into hydraulic pressure. If the driver of a car begins to feel sponginess in the brake pedal, it will almost certainly mean that the master cylinder has failed or is about to fail. It is suggested that a replacement component be fitted as soon as possible because the braking in the car has now been compromised. Having a worn brake master cylinder can be very dangerous and can be the cause of accidents due to not being able to stop the vehicle in time.