Vacuum brake booster: common defects and their signs

1. Depressurization.
   • Engine operation becomes unstable.
   • Hissing from the side of the component is heard during braking.
   • Engine vibrations at idle are increased.
   • Leakages of braking fluid are visible during visual inspection of the component.
2. Destruction of diaphragm or wear of valves rubber.
   • Handling of the vehicle worsened.
   • Braking efficiency decreased.
   • Whistling is heard during braking.
3. Fasteners loosening.
   • Knocking is heard from the side of the component during hard braking.
   • The brake pedal pushes back.

How to repair or replace vacuum brake booster?

Sometimes the part can be repaired. However, only professionals can estimate wear degree or allocate damages, so you need to apply to a service station for component diagnostics.

In most cases it is practical to replace the component. Common recommendations for single-handed replacement are the following:

1. Find a pull rod of the booster under the steering shaft and disconnect it from the brake pedal.
2. Then disconnect the brake master cylinder from the brake booster.
3. Disconnect the vacuum hose and the back valve of the booster.
4. Then demount the defective part, install a new one and perform assembling of all elements.

Peculiarities of replacement process may vary for different car models, so you need to look for the full list of recommendations in vehicle technical documentation.