Audi RS4 Brake Booster Replacement Cost

Normally, a vacuum booster will last from 150,000 miles to the lifetime of the vehicle. In especially dry climates, dry rot may cause deterioration of the internal diaphragm, and require replacement.

Diagnosing a vacuum or hydro-boost system is typically simple. The servicing technician may only need to feel the brake pedal with the engine running, and, noting the difficulty, immediately suspect brake booster failure. The booster will then be tested manually, and confirmed faulty upon failure of those tests. For vacuum boost systems, this means sucking the air from the booster, and observing pressure drop. For hydraulic systems, the hydraulic pressure going into the booster must be measured. If the pressure is within specification, yet the brake booster does not function, the technician will understand there is an issue with the booster, and recommend replacement.

Once a diagnosis has been reached, the brake booster must be disconnected from the vehicle by removing the master cylinder, brake booster vacuum or hydraulic lines, and finally the brake booster.

If the vehicle uses a hydraulic booster, it is recommended to flush the power steering system as the faulty brake booster may have allowed debris to travel through the system.

The brake booster bolts to the firewall directly opposite the brake pedal. Some manufacturer's have provided the bolts to remove the booster on the exterior of the vehicle, but others have placed the bolts behind the dashboard. The location of these bolts may negatively or positively impact repair cost, and time.

The braking system can be maintained by a DIYer with plenty of knowledge of hydraulic and vacuum systems. This is important as diagnostics and proper completion of the repair require this knowledge.