If the pedal does not "fall through", you should check the booster air filter. To do this, remove the rubber cover in the rear of the booster in the passenger compartment near the brake pedal and slide the cover along the rod.
Fig. 7.23. Replacing the brake booster air filter: A – air filter cut area; F – air filter installation location
Using a screwdriver, as shown in Fig. 7.23, remove the old air filter. Then, having made a cut in the new filter, install it in its proper place, making sure that it covers all the holes. Install the rubber cover and check the operation of the amplifier again.
Fig. 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 the check valve (Fig. 7.24), rotating it to remove it from the rubber seal.
Blow the valve, air should flow only in one direction - from the booster side. If the valve does not blow or blows in both directions, replace it. Check the condition of the rubber seal. Assemble the unit, connect the vacuum hose and check the operation of the booster.
If the amplifier still does not work, replace it, as the company does not supply a repair kit of parts.