BAS brake booster, component description - GF42.31-P-4004SX

MODEL 221.0 /1, 216.3 up to Model Year 8 

Location 

The brake booster is located in the left of the major assemblies compartment.

Task 

Like a conventional brake booster the brake booster assists the pedal force of the driver when braking but activates, in the case of emergency braking, the Brake Assist (BAS).

Design 

The brake booster contains the following electrical components:

• BAS diaphragm travel sensor
• BAS release switch
• BAS solenoid valve
• Brake fluid indicator switch

Function 

The brake booster is constantly supplied with vacuum via a vacuum line. When the brake is not operated the same vacuum acts on both sides of the diaphragm. A push spring holds the diaphragm plate in its starting position.

During the brake application outside air is lead to the back of the diaphragm via a port. Between the front and rear chamber of the amplifier a pressure difference occurs which acts in the direction of the master brake cylinder and thus assists the foot force.

In the event of emergency braking the brake booster is actuated by the ESP control unit via the BAS solenoid valve (N47-5).