The vacuum braking system consists of an intake manifold which supplies the necessary vacuum for the operation of the brake servo to which it is connected by a pipe and the pump also known as the master cylinder fitted on the brake servo.The pump is connected by two pipes, each of which suppiles a section of the crossover circuit, to the ABS electro-hydraulic control unit. (See subassembly ) 3340 ANTI-LOCK BRAKING SYSTEM (A.B.S.)On versions equipped with the ESP function, the pump and the control unit supply pipes are larger because this type of system has a greater fluid capacity.To facilitate servicing fitting operations, the pipes have a flexible section.