ok so its a 89 sedan. We replaced the booster and the problem we had went away but now the pedal is to the floor, we bled the brakes the correct way and still going down to the floor . Could this be the master cylinder . if so why ? i would like to understand the complete function and how difficult is it to replace. Thanks in advance.

 

Can you please describe what you mean by "going to the floor"?
Do you mean a gradual sinking to the floor if you hold your foot on the pedal? (typical master cylinder problem)
Or an instant pedal height issue when you first press down?

When you did this brake work, did you remove the master cylinder from the brake lines?
If so, then it is possible that you introduced air into the bore of the master cylinder (MC).
If this has happened, then you will have to remove the MC again and bench bleed it - Google can show you how.

If this was done and you are SURE you don't have air in the lines, then maybe consider a booster push rod adjustment.
If it is set too short, then your pedal will always travel farther down.
You will get consistent braking however the pedal will just be at the wrong height.
This is bad for the booster and not safe for you.

 

Thanks man. The pedal goes down when i go to push instantly. The car is hard to take off i think we need to try the bench bleed, the resevoir cam off in the process of changing the booster.