Seasons greetings everyone. Wondered if I could ask for some help. My 68 Fairlane 500 Fastback is having serious brake problems recently. This car has all new wheel cylinders, brakes. rubber brake lines and master cylinder and horribly has manual brakes. THanksgiving day my car was filled with fixins and I was headed to a family feast when I put my foot on the brake. My foot and pedal slowly went to the floor and I had to pump and down shift to finally stop. Later in the week I crawled under the car and did not see any leaks. I re bled the front brakes but have not yet bled the back ones. After taking mu car for another test drive nothing has changed. Still my foot goes to the floor. Does this mean that I was sold a defective master cylinder? Should I try to bleed the master cylinder again? I haven't been driving this car much since day 1 and the brakes have never been that great. I'm used to power brakes though so thought that this is how they are supposed to be. Any help would be greatly appreciated. Don't want to yoink and replace the master cylinder again if this problem could be something else. Many thanks for any help. This car is like a rocket on wheels so stopping correctly is of course my priority right now.