Checking the brake booster

Stop the engine, depress the brake pedal several times and hold it in the lowest position.

Start the engine. The pedal should move a few more millimeters. If not, the reason is as follows:

The vacuum hose from the intake manifold to the brake booster is leaking: in this case, be sure to replace the hose and check its connecting flanges.

Defective check valve in the vacuum hose: to check the valve, remove the vacuum hose from the brake booster and let the engine idle. If you do not hear rhythmic suction sounds, cover the free end of the hose with the pad of your finger. If there is no vacuum in the hose, the valve is defective.

Porous rubber gasket between brake master cylinder and brake booster: To replace, remove the brake master cylinder from the brake booster and replace the gasket.

The air filter on the hydraulic pusher of the brake booster is dirty: remove the filter from the hydraulic pusher with a wire hook. Cut the new filter down to the center and press it into place around the hydraulic tappet. Make sure that the filter closes around the pushrod, otherwise unfiltered air can enter the brake booster.

Amplifier membrane defective: repair is not possible. «make friends» with new brake booster assembly.