For 1990-2009 cars

### System Component Description

The brake assist system consists of the following:

Brake Pedal: Multiplies the braking effort applied by the driver.
Brake Pedal Pushrod: Transfers multiplied input force received from the brake pedal to the vacuum brake booster.
Vacuum Brake Booster: Uses source vacuum to decrease effort required by the driver when applying the brakes.
Vacuum Source: The source vacuum for a spark ignition engine is normally derived from the Intake Manifold.
Vacuum Source Delivery System: Enables delivery and retention of source vacuum for vacuum brake booster.

### System Operation

Under normal driving conditions, without the brakes applied, vacuum is allowed to act on both sides of the diaphragm within the vacuum brake booster. When the brake pedal is applied, the effort by the driver is multiplied due to the relative length of the brake pedal in relationship to its pivot point and the point at which the push rod to the Vacuum Brake Booster is attached. Movement of the push rod causes a valve within the Vacuum Brake Booster to close between the two sides of the diaphragm, thus isolating each side. It also allows a valve to open that allows atmospheric pressure to act on the pedal side of the Vacuum Brake Booster whilst maintaining vacuum on the vacuum source side of the diaphragm. The movement of the Brake Pedal Pushrod is transferred to the Hydraulic Brake Master Cylinder via the Vacuum Brake Booster. The pressure differential within the Vacuum Brake Booster reduces the effort required by the driver in applying the brakes.