Install the car on a flat area, raise the hood of the car and clean the regulator from dirt. External inspection makes sure that the pressure regulator is not damaged, the plug is recessed into the housing hole by 1-2 mm.
They ask an assistant to press the brake pedal, and they themselves insert a rod with a diameter of 6-8 mm into the socket of the protective cap and press on the end of the piston. When you press the pedal piston 14 (see fig. 119) should extend from the body by 1.75-2.5 mm, which will be felt by the fingers of the hand holding the rod. Before installing the rod, make sure that it does not have sharp edges that could damage the protective rubber cap.
If the stroke of the piston in the pressure regulator housing is not felt, this indicates a malfunction of the regulator. In this case, replace it.