Vacuum Brake Booster: Description and Operation

Brake Booster

COMPONENT LOCATION

NOTE:
Left-Hand Drive (LHD) shown; Right-Hand Drive (RHD) similar.









OVERVIEW
Power assistance for the braking system is provided by a vacuum operated, non-active brake booster.
The brake booster is a compact unit that occupies less space than a conventional brake booster, improving the vehicles crash performance characteristics. The unit is installed with tandem diaphragms that are 203.20 mm (8.00 in) and 228.60 mm (9.00 in) in diameter and operate as a single unit.
The unit is located on the driver's side of the engine compartment, and is sealed to the bulkhead with a gasket and secured with 4 studs and locking nuts. The brake booster actuating push rod is attached to the brake pedal with a clevis pin. The booster output rod locates in the primary piston of the brake master cylinder. For additional information, refer to Hydraulic Brake Actuation Description and Operation

VACUUM COMPONENTS
For both the i6 gasoline and TD4 diesel engines, the vacuum required for brake booster operation is created by a vacuum pump mounted at the rear of the cylinder head. The vacuum pump is driven by the intake camshaft.
A rigid plastic pipe connects the vacuum pump to a check valve installed on the front chamber of the brake booster. The pipe length and routing is different for LHD and RHD models.
The check valve maintains the vacuum necessary for brake booster operation and prevents air from entering the front chamber.

Stop/Start Vehicles - From 2010 MY

Stop/Start Vehicle Components









Brake vacuum sensor





A brake vacuum sensor is introduced on Stop/Start vehicles to monitor vacuum reserves in the brake servo. The vacuum sensor is mounted in the vacuum pipe and hardwired to the ECM. For additional information, refer to Starting System