Good day,
I have an old 2007 Taurus base model and the front pads got medal to medal and the rotor was fine as I caught right away and when I compressed the pistons back into the caliper the brake pedal starting going to the floor? it was fine until I pushed the piston's back in which has never happened to me in some 50 years of fixing my own stuff, I purchased a new Master Cylinder, bench blead the installed and and blead the system in the correct order still slowly goes to the floor and just to weed out other possibilities I adjusted the rear drum brakes but the didn't help either, what the heck could be the issue?
The car doesn't have traction control and I installed a non-traction control master cylinder any Ideas would be greatly appreciated.
Thanks,

 

Maybe this will help.
Normally,,,,,,,,,,,,,,,,,,,,,the brake pedal only goes down a certain distance with usual use. Garbage accumulates behind where the piston stops normally in the master cyl bore.
Now when you push the pedal down past that accumulation it scores the rubber cups inside the master cyl and they now allow pressure to bypass the scored cup and brake pressure is allowed to leak past the cup rendering the brake system ineffective. That said, now we go to "Modern brake systems" with anti lock provisions.

There are electrical solenoids that react to different braking conditions . Wheel speed sensors send info to an ABS module that tells the solenoids to open or close which affects how much braking pressure is applied to each wheel to prevent lock-up which can increase stopping distance.
When air gets trapped in an ABS system, it is very difficult to get it out completely without a scan tool to operate the solenoids. You very well may need to have the system bled with the use of a scan tool.
Please excuse the long winded explanation , but maybe the info will be helpful.

 

Hello
Might be better to have your original part repaired at https://www.upfix.com

Here is the service link
https://www.upfix.com/product-catego...odules-repair/

 

Questions, Questions, Questions.
Can we ask where did you get the replacement master cyl ?

I ask this because this would not be the first time someone installed a "New master cyl" that was defective right out of the box.

Unless a lot of air got into the lines, we acquire tunnel vision, "But its new and can't be defective". only to find that was the case. I have had quite a few of those !!
Some bleeder screws can be next to impossible to open after being exposed to road salt etc and can get wrung off while attempting to open them to bleed the component. Without the proper tools to repair , replacement of the wheel cyl or caliper is the only fix. Hope you were able to open all 4 bleeders.