hard pressed brakes

[michaeld]

I've got a 77 450 sel w/ 125k that has a clear issue w/ the brakes. The car stops, but it takes a very firm foot on the pedal before the brakes engage. Also, I hear the faint sound of escaping air pressure as I step on the pedal. I have a VERY tiny leak in my master cylinder, but it has been so small I haven't worried about it. Could a leak in a master cylinder be causing my symptoms? Ordinarily, I would attribute the "ffsssshhh" when I step on the brakes to a leaking brake booster, but I there is no mention of a brake booster in the Chilton manual. Is the master cylinder inegrated w/ the booster in this model? I would obviously like to fix my brakes before I bump into someone the hard way, but I don't want to replace the wrong part. Suggestions?

Also, anyone w/ the know-how to answer the above question can probabely answer an unrelated one regarding fuses for the same model: is there a good upgrade for the ceramic fuses? I have heard that corrosion is a problem w/ these ceramics.