Brake Assist System Description and Operation. Chevrolet Express 2001

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 2001 🢒 Express 🢒 Brakes 🢒 Hydraulic Brakes 🢒 Brake Assist System Description and Operation

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


(1)	Master Cylinder
(2)	Power Brake Booster Outlet Hose
(3)	Power Brake Booster Inlet Pipe/Hose
(4)	Hydraulic Brake Booster
(5)	Power Steering Gear Inlet Pipe/Hose
(6)	Steering Gear
(7)	Power Steering Cooler
(8)	Power Steering Pump

System Component Description

The brake assist system consists of the following:

System Operation

The hydraulic brake boost system uses fluid from the power steering pump (8) through the hydraulic boost inlet hose (3) and to the brake booster assembly (4). In addition to supplying the brake system with fluid for increased apply, the power steering pump is also connected to the power steering gear (6) and cooler (7).

The steering pump (8) is a continuous flow device supplying approximately 3 GPM at 1000 RPM, at the pump shaft. The fluid flows through the booster spool valve, then the return hose (5), and then to the steering gear (6). Pressure is produced by applying the brake pedal, resulting in the spool valve being actuated, internal to the hydraulic brake booster. The spool valve produces a marginal restriction that causes pressure in the booster (4) to rise and forces the power piston and therefore the output rod forward to generate force and motion at the master cylinder (1). The brake corners are actuated by the fluid impulse generated by the master cylinder (1). Internal blow by, or pressure relief, is directed to the low pressure return hose (2) back to the power steering pump (8).