[JP Noonan]

I'd tend to agree with Ascaris, the piston is seized. I don't know if I'd go as far as the caliper rebuild, unless they are leaking, but on the other hand these are the brakes we're talking about!

Try removing the caliper, put a piece of wood inbetween the pads. The wood should be a little thinner than the rotor (too thin and the piston will pop out spitting fluid in your eyes). Then have a helper push the brake pedal, if the pistons move freely in and out the pistons are most likely O.K. The reason for the wood to be a little thinner than the rotor is so the piston can pop past and corrosion build-up, hopefully for good. If the piston won't go back use a "C" clamp to return it into the caliper (be careful not to return it too far or fluid will leak out the resivoir up front) try this a few times to see if it frees up the piston. I did this on my 75 and it worked, not as good as re-built but the rears do work now.

If you need to rebuild them there are two kits out there, one has all the seals. On the other one you need to reuse the parking brake seal.