Hydraulic System: Description and Operation

Brake Warning System Description and Operation

Brake System Indicators

BRAKE
The IPC illuminates the BRAKE indicator and sends a class 2 message in order to activate an audible warning when the following occurs:
^ The IPC detects that the park is applied (signal circuit is low).
^ The IPC detects a low brake fluid condition (signal circuit is low).
^ The electronic brake control module (EBCM) detects a malfunction with the antilock brake system. The IPC receives a class 2 message from the EBCM requesting illumination.
^ The IPC detects a loss of communications with the EBCM and the discrete back-up ABS indicator signal is open.
^ The IPC performs the displays test at the start of each ignition cycle. The indicator illuminates for approximately 3 seconds.

CHECK BRAKE FLUID - 37
The IPC illuminates the CHECK BRAKE FLUID- 37 indicator in the DIC and sends a class 2 message in order to activate an audible warning when the IPC detects that the brake fluid level is below the normal operating range.

Hydraulic Brake System Description and Operation

System Component Description
The hydraulic brake system consists of the following:
Hydraulic Brake Master Cylinder Fluid Reservoir: Contains supply of brake fluid for the hydraulic brake system.
Hydraulic Brake Master Cylinder: Converts mechanical input force into hydraulic output pressure. Hydraulic output pressure is distributed from the master cylinder through two hydraulic circuits, supplying diagonally-opposed wheel apply circuits.
Hydraulic Brake Pressure Balance Control System: Regulates brake fluid pressure delivered to hydraulic brake wheel circuits, in order to control the distribution of braking force. Pressure balance control is achieved through Dynamic Rear Proportioning (DRP), which is a function of the ABS modulator.
Hydraulic Brake Pipes and Flexible Brake Hoses: Carries brake fluid to and from hydraulic brake system components.
Hydraulic Brake Wheel Apply Components: Converts hydraulic input pressure into mechanical output force.

System Operation
Mechanical force is converted into hydraulic pressure by the master cylinder, regulated to meet braking system demands by the pressure balance control system, and delivered to the hydraulic brake wheel circuits by the pipes and flexible hoses. The wheel apply components then convert the hydraulic pressure back into mechanical force which presses linings against rotating brake system components.

Brake Assist System Description and Operation

System Component Description
The brake assist system consists of the following:
Brake Pedal: Receives, multiplies and transfers brake system input force from driver.
Brake Pedal Pushrod: Transfers multiplied input force received from brake pedal to brake booster.
Vacuum Brake Booster: Uses source vacuum to decrease effort required by driver when applying brake system input force. When brake system input force is applied, air at atmospheric pressure is admitted to the rear of both vacuum diaphragms, providing a decrease in brake pedal effort required. When input force is removed, vacuum replaces atmospheric pressure within the booster.
Vacuum Source: Supplies force used by vacuum brake booster to decrease brake pedal effort.
Vacuum Source Delivery System: Enables delivery and retention of source vacuum for vacuum brake booster.

System Operation
Brake system input force is multiplied by the brake pedal and transferred by the pedal pushrod to the hydraulic brake master cylinder. Effort required to apply the brake system is reduced by the vacuum brake booster.

Brake Booster Pump

Description and Operation (Right Drive)
The power brake booster pump supplies the hydraulic pressure needed for power assist braking. The power brake booster system supplies hydraulic pressure to the hydraulic brake accumulator after the accumulator is discharged. When more hydraulic pressure is needed in the accumulator, the power brake booster pressure switch closes, energizing the power brake booster pump relay. The power brake booster pump motor runs to supply the additional hydraulic pressure to the accumulator.