You need to apply and release the brake pedal several times until the pedal becomes firm to deplete the
Brake Booster vacuum reserve and disconnect the power vacuum brake booster vacuum hose and check valve. Then you need to remove the master cylinder assembly, the knee bolster, the brake booster pushrod retainer, the brake booster pushrod clevis pin, and the power vacuum brake booster nuts. After that, you need to remove the power vacuum brake booster. Finally, you need to remove the power vacuum brake booster gasket, inspect the gasket for damage, and replace it if necessary.