Hummer H3. Manual — part 1344

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 dynamic rear proportioning (DRP), which is a
function of the ABS modulator. Refer to ABS Description and Operation for specific
information on the operation of DRP.

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

2007 Hummer H3

2007 BRAKES Hydraulic Brakes - H3

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 accumulator fluid pressure created by the pump and motor to decrease effort required
by driver when applying brake system input force.
When brake system input force is applied, pressurized brake fluid is admitted to the rear
chamber of an apply piston, providing a decrease in brake pedal effort required. When input
force is removed, pressurized brake fluid is blocked off from the piston.

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.

SPECIAL TOOLS AND EQUIPMENT

SPECIAL TOOLS

Special Tools

Illustrations

Tool Number/Description

CH-47830

Holding Fixture

2007 Hummer H3

2007 BRAKES Hydraulic Brakes - H3

J-28662

Brake Pedal Effort Gage

2007 Hummer H3

2007 BRAKES Hydraulic Brakes - H3

J-29532

Diaphragm Pressure Bleeder

J-35589-A

Master Cylinder Bleeder Adapter

2007 Hummer H3

2007 BRAKES Hydraulic Brakes - H3