1988 Town Car brake problem

having problems with my brakes. The pedal goes down to the floor and the car is very hard to stop. I replaced the master cylinder and still the same
thing. I'm wondering if the vacuum booster is going bad due to the fact that I sometimes hear which sounds like air coming from behind the dashboard when applying brakes. I checked the line itself, the engine speed decreases when I put my finger over the hose. I'm also wondering if it might still be some air in the brake lines?
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If you didn't bleed the brakes until bubbles and clean fluid came out after the master cyl. change, air is a good suspect. I hope you are using some type of service manual for the work. It should tell you the proper way to bleed brakes. I always invert a fresh bottle of fluid in the master cyl. and then bleed the right rear first. I used to flush brakes every coulpe of years to be sure moisture isn't a problem.
A "whoosh" when hitting the brakes is normal, there is a rubber bellows on the lever at the firewall. The vacuum side of things is under the hood. Even if the brake booster had no vacuum, the pedal wouldn't go to the floor. It would be very hard to puch right from the start but it would be solid.
What led you to replace the master cyl. to begin with?
PoD

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The reason for the original change was the brake pedal started all of a sudden going to the floor. I also repleced the front pads because it was near that time.

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So it would seem the problem remained after the change. Hmmm... I expect you have checked for leakage so we can bypass tube replacement and such.
I found that any time I had a soft pedal, flushing the system usually fixed it. It is the same as bleeding the brakes, just more of it. Bleeding works best with a helper unless you have a machine to help. Always do the furthest wheel first. On this car, I would do the right rear, then left rear. Right front, then the left front. Be sure the fluid doesn't get low in the master cyl. I think I mentioned earlier, I invert a fresh bottle of DOT3 in the proper chamber before starting.
I had a car not too long ago that had frozen rear pistons. It was drum brakes on the rear and a new assembly for each side was quite cheap. That made a huge difference in stopping but the pedal never went soft or hit the floor.
I am running out of ideas here - I think better when I am staring at the machine in question - . Bleed / flush the brake lines would be the next step for me...
PoD

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I forgot to ask, does the car have ABS (Anti-lock brakes)?

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Found out the problem. There was still air in the system and I also had to replace a leaking brake line and heat up the bleeder valves on the rear drums to get them off.
Thanks everyone for their help and suggestions.

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Good Job!! I'm glad you found it!
PoD

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