Brake System Inspection

Remove the wheels and drums; inspect brake friction materials, master cylinder, brake lines, calipers and wheel cylinders.

Typical Car and Truck Brake Systems Basic Operation

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 (Anti-Lock Brake System) 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.


The two primary types of brake systems are anti-lock brake systems (ABS), and non-ABS. ABS are designed to ensure more vehicle stability by changing the fluid pressure to automatically pump the brakes, preventing them from locking up. With non-ABS brake systems, the driver must pump the brakes to prevent lockup.
Brake Action

When the the brake pedal is depressed, this causes a push rod within the master cylinder to force out fluid. This travels through the brake lines to the wheel cylinders. If the vehicle has disc brakes, the brake fluid flows into a caliper and presses against a piston, which then squeezes brake pads against the wheel rotor. If the car has drum brakes, the fluid pushes the brake shoes so that there is friction against the wheel.

A key feature of brake systems is that the brake fluid is incompressible, transferring pressure to the brakes.
There can’t be any air in the fluid for brakes to be effective.