[papajam]

If the pedal comes up high and hard with one pump, that pretty much rules out air being in the system. Air will usually result in a consistantly low, spongy pedal no matter how many times you pump the pedal.
Sounds like you have either caliper piston knock-back (the wheel bearings are too loose) or cal piston pull-back (the cal piston seals are hard with age and are pulling the pistons back too far into the caliper).