The main brake cylinder
Brake master cylinder converts mechanical force applied to the pedal, and a fluid pressure is to simultaneously create pressure in both circuits the hydraulic actuator when the pedal is depressed.
In all versions of the car double-cavity Sharan set brake master cylinder with a serial arrangement of the pistons. The main body of the master cylinder reservoir is mounted in the filler neck which sensor is installed emergency brake fluid level.
When you press the brake pedal pressure is created simultaneously in both circuits hydraulically by two pistons of the master cylinder: pressure piston (nearest to the push rod) drive circuit "left front - right rear brake" and the intermediate piston drive circuit "right front - left rear brake ".
The main brake cylinder and can not be repaired in case of failure is replaced by a new one.
If you need to brake suddenly become a much larger force, and braking distances become longer, the reason for this is almost certainly a failure of one of the brake circuits of the drive.