2398687 - 3330D brake vacuum system

GENERAL VIEW1 - Brake pedal 2 - Brake servo 3 - Intake manifold 4 - Brake control pump 5 - Vacuum connection pipe The brake vacuum system consists of an intake manifold, which supplies the vacuum necessary to operate the brake servo (to which it is connected by a pipe) and the control pump or master cylinder fitted to the brake servo. The pump is connected to the ABS hydraulic control unit by two pipes, each of which supplies one section of the cross-over circuit  Characteristic of working principle 3340  A(B.S. ANTI-LOCK BRAKING SYSTEM .). On versions with ESP, the pump and control unit inlet lines are bigger because the fluid flow is higher through this type of system. The pipes include a flexible section to facilitate fitting operations during service. The system makes the braking action smoother and more powerful through the action of the brake servo. The brake servo is a pneumatic device that uses the vacuum set up in the intake manifold to make the brake pedal act more powerfully on the pump so that braking action can be modulated more effectively.If the vacuum system should fail, brake system operation is still ensured because the connecion between operating pedal and brake control pump remains operational.

Under such emergency conditions, the brake pedal becomes very hard to operate and braking action is not as prompt. It is therefore advisable to drive with extreme care to the nearest authorised service outlet to check the system.