Clutch has no pressure 1991 brettea gtz

Hello: sounds like you have a hydraulic clutch linkage mechanism, thats to bad, the old mechanical kind always worked. Well two possibilities. The master cylinder for the clutch is shot, or the slave cylinder for the clutch is shot. If you have a hydraulic throw out bearing then is would be the same as a slave cylinder. You did not say if the clutch works properly or not. If the clutch appears to work properly but seems pedal pressure had dropped, then I would suspect the pressure plate has lost some of its spring pressure ability. This may cause the clutch to slip more than usual it would seem.
Good luck
Darryl.