[4pilgrim4]

I'd put my vote on a bad master cylinder, too, since I've had a couple go that route.

One way to tell is if the fluid level is pretty much to the proper level, it's just about gotta' be the MC. If the MC is empty, then it's leaking somewhere.

Repeated filling and pumping will only saturate your brake linings with brake fluid if a wheel cylinder is bad and render them useless. However, they are likely worn enough to replace anyway - and they're not a big ticket item, nor is a wheel cylinder or a master cylinder - especially if you do your own work.