2006 Chevrolet Monte Carlo Brake Booster

The procedure is to remove the Brake Master Cylinder, secure the mounting flange of the brake master cylinder in a bench vise, clean the outside of the master cylinder reservoir on and around the reservoir cap, remove the reservoir cap and diaphragm from the reservoir, inspect the reservoir cap, remove the master cylinder reservoir, depress the primary piston, remove the piston retainer, remove the primary piston assembly, plug the cylinder inlet ports and the rear outlet port and discard the primary piston assembly, the piston retainer, and the seals and seal retainer.

You should press the brake pedal to inspect for firmness.