2009 Mercedes-Benz ML350 Parking Brake System Adjust Cost

The parking brake is used to secure the vehicle while the vehicle is not in motion and unattended. It is typically secured by using a lever in the vehicle to pull the parking brake cable which sets the brake. Many modern vehicles are moving to an electronic parking brake, which uses an electric motor to set the parking brake when the driver presses a button. Adjustments are necessary when the brake no longer holds the vehicle, or if the parking brake is causing braking force while driving.

There are a few different types of parking brakes, but they are all actuated in the same way. A lever or electronic switch in the vehicle is pulled or pressed, and this will either pull the parking brake cable or signal the parking brake motor to set the brake. Whether or not the vehicle uses a park brake cable or park brake motor, using the lever or button will cause the park brake to secure the brakes, normally at the rear wheels. Drum brake and auxiliary drum brake vehicles will press the brake shoes out against the inner liner of the brake drum, and disc brakes without auxiliary brake drums will squeeze the brake pads against the brake rotor.

It may seem obvious that the only issue a parking brake can create is that it does not hold the vehicle, or does not release the wheels. However, there are several other indicators a technician will look for when diagnosing these two symptoms. The park brake lever may have no tension when pressed, there may be brake noise when driving the vehicle, the electronic park brake button may not be illuminated, or the sound of the relay clicking is not heard when the button is pressed, and there may be physical damage evident upon inspection. All of these symptoms will point to a likely cause during inspection.