I have bled the lines more times then I care to count. I replaced the MC twice and extended the MC push rod about as far as it is aloud. I adjusted the brake shoes but the brake pedal still goes to the floor. I am going to replace the front brake hoses today and see if that helps but if it doesn't I can only replace the back hose and then I'm out of my territory.It is drums all around. I put http://www.partsamerica.com/productd...Number=5473202in it but dont know if this is he prob. Any idea? Thanks

 

Be more specific about the brake pedel going all the way to the floor. Do you feel any resistanace. If you repeatedly pump the brakes do they build up pressure? What method are you using for bleeding the brakes? If you have a helper press the pedel while you crack open the valve do you get a good flow of fluid? Are you loosing fluid from the master cylinder when you try to operate the brakes?
Unless you're seeing some sign of leakage of the brake lines, I doubt replacing them will fix your problem.
Were they power brakes to start with? You're post makes it sound like you added the power booster; was it a replacement?

 

The car had power brakes when I bought it back in Sept but I don't know if the car originaly came with them becuase when I replaced the booster, it had a piece welded on the end of it to extend it to where it connects to the brake pedal. I was told my old brake booster had a vacuum leak so I bought a new one.I used a helper to bleed the brakes like you described and I get a good flow from all lines. I don't see any leaking nor do I lose fluid in the MC after everything is tight. The pedal has great resistance and pressure when the booster is off but as soon as I start the car or hook up the vacuum hose the pedal loses everything and goes to about 1 inch from the floor. I can only think that maybe my hoses are flaring up but I don't see any bulge when brakes applied. I don't know what else to try and it's not like I can drive it somewhere to get it fixed. I think it has to be the brake booster but don't know how to correct it. Thanks

 

Definitely sounds like the problem has to do with the booster. I know the booster is new, but.... since you replaced the MC twice I assume you have experience with new parts not working.
The "modified" rod gives me some concern. I would first try to get a picture of a stock rod for comparison, or may be post a picture of yours for comment.
Did you make a detailed comparison between the booster you removed and the one from the store? The reason I ask is that the previous owner could have used one of the power brake conversion kits that were "designed" for manual brake pedals. If you swapped in a stock style unit then the rod could be pushed further into the booster unit causing havoc. Another thing to check is the mounting point for the brake pedal. The power mounting point is higher than the manual mounting point. I'm just throwing out ideas since it appears you have covered the standard bases.
You might check over at the MustangSteve forum. Scott is having very similar problems to yours.