fastback brake problem

[thrash911]

hi quick question from the uk, ive got an 86 fastback gt, car drives nice but has the odd problem, main one being the brakes. pads are all ok, calipers are free, no sticky pistons or sliders etc, pedal is spongey as hell and wont lock the brakes up no matter how hard I press the pedal. I thought it was the brake fluid so yesterday I flushed the lot and replaced with new, got a little better but still not as good as I think they should be, ive heard that the brakes are the Achilles heel of the fiero. any recommended upgrades or ideas, don't want to replace all the calipers as they seem to work, thinking it maybe the master cylinder.

 

[melsg5]

If you can get your hands on a master cylinder rebuild kit, might be a good idea to try that since you have no leaks or air in system.