Ford Repair: Brakes, mercury cougar, rear brakes

Question
"I have an 1989 Mercury Cougar; the brakes went out so the first thing I did was:
1. Changed front & rear brakes
2. Rear Cylinder (they were leaking)
3. Visually checked for pin holes in brake line
I bled the brakes after each step and I still had very very little brake. Now I don't know what to do, since I've never ran across a problem like this before. When I'm bleeding the brakes I keep getting an excessive amount of air, as if I'm pumping air into the brake line somehow. My brother in-law said something about a vaccuum cylinder, I don't know what he is referring to, do you? Another question is can the master cylinder allow air into the brake line? That is the only thing I can think of that I have not replaced; and if there is a pin hole in the line, that I cannot see visually, is there a way to check that and if so, do I have to replace the line or can I patch the brake line? Thanks for reviewing my question and I would appreciate any feed back you give me on this. Thanks Jay";  

Answer
Hi Jay,
It sounds like your master cylinder is bad. Replace it and bleed the brakes. Air can't get into the system through the lines. If the lines are bad, brake fluid will leak "out". Make sure your rear brakes are adjusted up. The vaccuum cyl your brother in law is refering to is the brake booster. The master cylinder is mounted to it. It is operated by vaccuum. It assists in braking. If you have a rock hard pedal, the booster is bad.
GOOD LUCK!

Jeff
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