1992 Mitsubishi 3000GT clutch not holding pressure. I NEED

I have a 92 mitsubishi 3000gt fwd 5spd, I was driving and clutch just lost pressure. I had to manualy lift the pedal from the floor. Before then I have never had a problem with the clutch slipping or anything even at high rpms, in fact it had a new clutch plate, pressure plate, throw out bearing, ec. Installed at 118000 miles. I have put in a new clutch kit, and transmission ( because syncronizers were out in 5th and reverse). I lined up the clutch with the line up tool, mounted the transmission, and when I tried to put in in gear it grinded (clutch still does not have pressure) althought it will go in gear if I pump the pedal. I tried bleeding it numerous times, but it only has pressure when I pump it for a while. I am almost certian it is the master cylinder because of loss of pressure and not leaking, plus the clutch just going out out of the blue, working perfect ant less than 10mins later no pressure. ANY ADVICE WOULD BE GREATLY APPRECIATED. I NEED A RIDE TO WORK