perhaps it's the master replacement that caused the trouble. the brake master resevoir feeds the clutch master cyl. it's very possible air got into the clutch system. there's a bleeder screw on the slave cyl on the transmission. push the pedal, open the screw, close the screw, raise the pedal. repeat until pedal feel returns. takes 2 people. try that. if that doesn't make it work, then REPLACE BOTH the clutch master and slave cyls. a new master against an old slave and vice versa will make the other leak. good luck, chuck.