2427422 - 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, (diesel versions come with a vacuum pump as well), which supplies (when the engine is running) 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  See subassembly 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 (when the engine is running), or vacuum pump for the diesel, 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.

In emergency situations, the action on the brake pedal becomes very tiresome and the braking system does not maintain the same responsiveness properties. It is therefore advisable to drive the vehicle extremely carefully to the nearest authorized workshop to have the system checked.