Brake Booster Replacement
What is a brake booster?
The brake booster sits between the brake pedal and the master cylinder, and uses vacuum or hydraulic pressure to assist the driver when the brakes are applied. The most common type is the vacuum booster, a round drum that is mounted under the hood directly in front of the driver’s seat.
How does the brake booster work?
Brake boosters operate by multiplying the force applied to the brake pedal. When the brake pedal is pressed, it pushes a rod into the brake booster. Then, the brake booster instantaneously pushes the master cylinder with much greater force, allowing the driver to press the brakes with ease, yet creating a great deal of stopping power.
When a brake booster is defective, the effort required to stop the vehicle may increase significantly and the vehicle may idle roughly. Also, there may be a loss of vacuum, which is necessary to operate other systems such as heating, ventilation, air conditioning, and cruise control.
The Check Engine Light may illuminate with a P0171 or P0174 code, which indicates that the fuel system is running too lean due to a vacuum leak in the brake booster.
What are the symptoms related to a bad brake booster?
When the brake booster fails, the braking pressure needed at the brake pedal increases dramatically, and, in some cases, the brakes may seem unresponsive. For vacuum boosters, failure will generally create a vacuum leak, and the vehicle may run roughly, become hard to start, misfire at engine idle, and exhibit poor fuel mileage. The check engine light may also illuminate, and OBD trouble codes for engine misfires, lean air/fuel mixture, and intake manifold pressure will be stored in the computer. If the brake system uses they hydro-boost system, there will likely be a power steering fluid leak on the ground, and the brakes will be very difficult or impossible to press.