Hydraulic System: Description and Operation

Brake Warning System Description and Operation (DRL Equipped)

Brake Warning Indicator
The Brake Warning Indicator illuminates when the when one or more of the following occurs:
^ The EBCM performs the bulb check. The EBCM applies ground to the ABS pressure differential sensor signal circuit.
^ The brake pressure differential switch is closed by a pressure differential between the front and rear brake circuits. The brake pressure differential switch applies ground to the ABS pressure differential sensor signal circuit.
^ The power brake booster fluid flow and pressure are detected as being low (w/UJ1 Only). The power brake booster fluid pressure and fluid flow alarm switches both close, applying ground to the brake fluid level sensor signal circuit. In turn, the P/B Booster Fluid Flow And Pressure Alarm Delay Module applies ground to the brake warning indicator supply voltage 2 circuit. The power brake booster fluid flow alarm also sounds when this occurs.
^ The park brake is engaged. The park brake warning switch applies ground to the park brake switch signal circuit. In turn, the Daytime Running Lamps (DRL) Control Module applies ground to the brake warning indicator control circuit.
^ The ignition is turned to START. The ignition switch applies ground to the park brake switch signal circuit. In turn, the DRL Control Module applies ground to the brake warning indicator control circuit.

Brake Warning System Description and Operation (Without DRLs)

Brake Warning Indicator
The Brake Warning Indicator illuminates when the when one or more of the following occurs:
^ The EBCM performs the bulb check. The EBCM applies ground to the ABS pressure differential sensor signal circuit.
^ The brake pressure differential switch is closed by a pressure differential between the front and rear brake circuits. The brake pressure differential switch applies ground to the ABS pressure differential sensor signal circuit.
^ The power brake booster fluid flow and pressure are detected as being low (w/UJ1 Only). The power brake booster fluid pressure and fluid flow alarm switches both close, applying ground to the brake fluid level sensor signal circuit. In turn, the P/B Booster Fluid Flow And Pressure Alarm Delay Module applies ground to the brake warning indicator supply voltage 2 circuit. The power brake booster fluid flow alarm also sounds when this occurs.
^ The park brake is engaged. The park brake warning switch applies ground to the brake warning indicator control circuit.
^ The ignition is turned to START. The ignition switch applies ground to the brake warning indicator control circuit.

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 front-rear 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 a combination valve.
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 (Vacuum Assist)

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 Assist System Description and Operation (Hydraulic Assist)

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.
Hydraulic Brake Booster: Uses power steering fluid pressure to decrease effort required by driver when applying brake system input force. When brake system input force is applied, pressurized power steering fluid is admitted to the rear of an apply piston, providing a decrease in brake pedal effort required. When input force is removed, pressurized power steering fluid is blocked off from the piston.
Power Steering System: Supplies pressurized power steering fluid used by hydraulic brake booster to decrease brake pedal effort.

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 hydraulic brake booster.