312002028 - Introduction

Introduction

The vacuum braking system consists of:

• intake manifold (for versions with petrol engine), which provides (with the engine running) the vacuum required for the operation of the brake servo;
• vacuum unit (on versions with diesel engine) which receives the power from the camshaft controlling the inlet valves and produces the vacuum required for the operation of the brake servo;
• a pipe connected to the brake servo;
• control pump, also known as the master cylinder, fitted on the brake servo.

The pump is connected by two pipes, each of which supplies a section of the crossover circuit, to the ABS electro-hydraulic control unit.    See descriptions 3340 ANTI-LOCK BRAKING SYSTEM (ABS) The vacuum unit fitted on the 1.3 Multijet engine is illustrated below.1. Vacuum unit2. Vacuum intake3. GasketThe connection from the vacuum unit or from the intake manifold to the brake servo is illustrated below.1. Vacuum intake pipe2. Valve on the brake servo3. Brake servo4. Brake pumpThe system offers smoother, more powerful braking through the action of the brake servo. The brake servo is a pneumatic device which, using the effect of the vacuum created inside the intake manifold (with the engine running), provides power for the brake pedal action at the pump and allows smoother braking.If there is a problem with the vacuum system (or with the engine not running), the operation of the braking system is guaranteed because the connection between the pedal and the brake pump remains operational.

In these emergency conditions, the action on the brake pedal becomes very tiresome and the braking system does not maintain the same responsiveness.