I have been trying to track down a problem I am having. It is disk front and drum rear. New Pads, shoes, drums, rear wheel cylinders, new fluid and bled brakes multiple times.
Here is what happens.
If driving the car normally and hit the brakes 1 time, pedal feels ok and stops ok if not trying a panic stop. If you let off of the brake while slowing and press the pedal a 2nd time, then the pedal goes half way to the floor and have very little braking power. The brakes seem to be ok when you only touch them 1 time. I am leaning towards a master cylinder but am looking for opinions but usually that would increase braking by pumping the brakes. This actually works the opposite. Thanks for any ideas you might have.

 

Just an update. Put in a new master cylinder and that seems to have fixed the problem.