Alright I'm pretty sure I've been through every thread on this and haven't found any helpful info. My brake pedal goes all the way to the floor and has to be pumped to stop/slow down, once pumped up it works great for a few minutes then goes back to being a bitch. I replaced the master cylinder, checked all brake pads and been bleeding the lines for the last 2hrs (no air coming out) what could be causing this?!

 

First adjust your rear brake shoes (if you have inspected them and the slave cylinders don't leak)

 

Yes, make sure your rear brake shoes are properly adjusted.

Are there any leaks? Now is the time to check.

I would not rule out the possibility of a bad new master cylinder yet.

 

Did you bleed your master cylinder before installing? If not, no matter how much you bleed your brakes you will not solve the issue.