Immediately after replacing my defective master cylinder and bleeding the brakes, I ended up with a hard pedal about half way depressed but Limited braking effect! I doubt it is the booster, since it was working fine prior to replacing the master cylinder. Could the issue be related to the fender mounted small brass electric powered slider valve (Brake System Warning Valve) attached to the hydraulic lines just beneath the brake master cylinder? I had disconnected its one wire prior to bleeding, as directed in the shop manual and then reconnected after. Yes, I bench bled the master prior to installing and the reservoirs are full Presently, the Brake Warning Light is illuminated and the car is not safe to drive in traffic. Hopefully, someone has an solution.