A1 Cardone 10-4480 Master Cylinder 100% computer testing ensures guaranteed, consistent performance 100% new OE-quality seals and cups are installed to prevent leakage and ensure like-new performance and reliability. All rubber meets S.A.E. specifications Bleeding tubes are supplied with applicable applications to make the bleeding process faster and easier Bores meet critical micro-finish specifications to eliminate pitting and corrosion, which could cause premature failure Cast iron master cylinders come with premium protective coating to minimize rust, extending on-car and on-shelf life The first step to bench bleeding a step bore is to slowly depress the master cylinder piston, then release slowly and wait 20 seconds before depressing again. NEVER pump piston/pedal with a step bore style master cylinder. Follow the same process on the vehicle. Check booster for a defective push rod seal. If this seal is bad, it could drain the brake fluid out of the master cylinder.