99 S10 Blazer 4x4 Rear Brake Problems

[bwood]

Working on my Mom-n-Laws Blazer, did new disc and pads all around (4 wheeel disc). Her rear disc pads were chewed up and I replaced the rotors as they were pitted bad from the factory. I put it all back together and took it for a drive. The rear calipers are dragging pretty bad, probably why they were in such bad shape, the truck only has about 60k on it. Its not the parking brake, it is loose and working properly. Its got to be the center rear brake line or the master cylinder for both to be screwing up. I've drug on this far to ask if there are any known issues on these trucks with the master cylinder? Neither are a big deal to me, but its her money I have to spend, so I want to hit the nail on the head the first time. I'm going to try and blead as much as I can and get some fresh fluid in it as the master cylinder looks pretty nasty. Anyway looking for any pointers, its been awhile since I've done any work on the S Series trucks, I used to have a 99 and a 91.