If the pedal «does not fail», you should check the air filter of the amplifier. To do this, in the passenger compartment at the brake pedal, remove the rubber cover at the rear of the amplifier and slide the cover along the stem.
Pic. 7.23. Replacing the brake booster air filter: A - air filter notch zone; F - air filter installation location
Using a screwdriver, following fig. 7.23, remove the old air filter. Then, making a cut in the new filter, install it in place, making sure that it covers all the holes. Replace the rubber cover and check the amplifier again.
Pic. 7.24. Brake Booster Check Valve: 1 - valve; 2 - rubber seal
If the result is unsatisfactory, try replacing the booster check valve. To do this, disconnect the vacuum hose from the vacuum booster. Pull out check valve (pic. 7.24), rotating it to remove it from the rubber seal.
Blow out the valve, air should flow only in one direction - from the side of the amplifier. If the valve does not purge or purges in both directions, replace it. Check the condition of the rubber seal. Assemble the assembly, attach the vacuum hose and check the operation of the amplifier.
If the amplifier does not work again, replace it, as the company does not supply a repair kit for parts.