jmbeam, the proper caliper bleeding sequence is RR, LR, RF, LF. If you bled the calipers in some other order you could have trapped air in the system resulting in a spongy feel to the brake pedal. It's also possible that if you had a helper press the brake pedal while you bled each caliper that the master cylinder was damaged inadvertently because the piston went beyond its normal travel range, or if the bleed fitting was not closed while the brake pedal was depressed air could have been sucked into the brake line(s). That's why it's best to use a pressure bleeder.

Recommend bleeding the system again before considering replacement of the master cylinder.

__________________
Fred Hoelzle