I recently replaced a master cylinder on a 99 Civic Sedan because the brake pedal would travel to the floor hardly engaging the brakes at all.

Bought a new Fenco MC from Autozone, bench bled it, and bled all 4 corners with no results. Pedal still feels the same. It builds up pressure after repeatingly stepping on it with the car off. After turning the engine on, the pedal goes straight to the floor.

Just looking for ideas what to troubleshoot next. There's no leaks in the lines. Fluid in MC remains the same. Thanks

 

I had that problem on my ef hatch and it was a bad set of shoes in the rear drums. Put in new shoes, adjusted them, and it was fixed. Of course I bled the brakes half a dozen times before thinking to check the rear shoes, since they were only a few events old, but I had a fault pair or a sticky wheel cylinder and on one side the shoe material was completely disintegrated.