How do you rebuild a brake booster

Check the brake booster for defects and have it replaced

Brake booster defective - sources of error, inspection and replacement in the workshop

The job of the brake booster is self-explanatory. Since the foot pressure on the brake pedal alone is not enough to build up enough brake pressure in the system, this work is done by the brake booster. Experience has shown that a brake booster rarely has a defect. But if the brake pressure decreases, you should urgently look for the causes and also check the brake booster for a defect. At FairGarage you will find specialist workshops in your area that will reliably check the brake booster and change it at a fixed price. You can now compare the costs for your car without obligation and arrange the desired date directly online.

Function of the brake booster

If the engine compartment is not completely covered, the brake booster can be easily identified. The can-shaped, vertical component, mostly painted black, is located on the driver's side, near the partition wall to the passenger compartment. A flexible membrane sits inside this can. The running engine supplies the brake booster with negative pressure via the throttle valve (gasoline engine) or a vacuum pump (diesel engine). When the brake pedal is pressed, the driver's foot pedal force is increased by the negative pressure. This increases the brake pressure on the wheels. The amount of force generated in this way depends on the diameter of the membrane. Brake booster, brake cylinder and expansion tank form a compact unit in the engine compartment.

Sources of error with a defective brake booster

Correct functioning of the brake booster requires a hermetically sealed system. Defects in the brake booster can have various causes. Before changing, you must therefore check hoses, sleeves, valves and supply lines to the brake booster. They can be damaged by wear and tear, soiling and the weather. Hoses chewed on by animals can also cause failure. On the brake booster itself, corrosion on the housing or old seals can cause problems over time if air or residual water penetrates.

Defects, their effects and correct testing

If the brake booster refuses to work, this can be determined relatively easily; even technical laypeople can check the brake booster or simply identify a defect. The car can still be braked with a broken brake booster. However, the force required for this, i.e. the pressure on the pedal, is much higher. The high amount of effort required when the engine is running is only one symptom of a defect in the brake booster. A brake pedal that is difficult to depress when the engine is switched off can also indicate a defective brake booster. Furthermore, if there are leaks in the seals or if there are rust holes in the housing, the brake booster may hiss with a clearly audible hiss. This hissing sound is caused by the negative pressure that pulls air into the brake booster housing.

An overview of the signs of a defective brake booster:

  • The force required for braking is much higher;
  • It is difficult to depress the brake pedal when the engine is switched off;
  • Clearly audible hiss of the brake booster;

Have a specialist change the brake booster

If there is a defect in the brake booster, only an exchange in the specialist workshop will help. After all, the brake booster is a safety-relevant component. Changing requires specialist knowledge and is by no means a task for hobby screwdrivers. In order to be able to change the brake booster, work on the sensitive master brake cylinder is required. In addition to removing and installing the brake booster, the scope of work also includes changing the brake fluid and properly bleeding the entire brake system.

The cost of changing a defective brake booster

Duration and costs can vary widely and also depend on the type of vehicle. The costs also depend on whether the master brake cylinder is also changed. The spare parts cost an average of 250 euros for the brake booster, another 180 euros for the master brake cylinder and the cost of changing the brake fluid. In addition, there are working hours in the workshop. But as with all repair and service work, you can calculate the exact price for this work on your vehicle at FairGarage and arrange a suitable workshop appointment right away.