The front brakes were squeaking so I changed the pads. I bled them until there was no air. Then the brakes were not working well. You had to push the pedal all the way to the floor and it would barely stop the car. There was no sponginess or anything and it did not pressure up if you pumped it. I tried to bleed more fluid and that did not help. I changed the calipers and then there were no brakes at all. They go right to the floor with no resistance or sponginess. I then tried to change the master cylinder and it did not help at all. I am out of ideas.
Assuming there's no air trapped in the system and calipers and the master cylinder are functioning properly, I'd suggest to check the following things:
- Brake hoses. They are made of elastic material and sometimes have an inner structure damaged even if there are no visible leaks. Have someone to help you by pushing a brake pedal while you're inspecting the hoses. You should look for a bubble-like expansion of rubber.
- Solid metal brake lines. If they have cracks you would notice brake fluid leaks under the car after pushing the brake pedal several times. It would also drain a brake fluid reservoir.