I have a 1992 GMC C2500. When I got it there was no pressure at all in the clutch. I bleed it from the bleed valve for about 20 minutes to make sure there was no more air bubbles coming out. After all that there is still no pressure to the clutch. Does anyone know what might be the problem and how I can fix it? Also when i got it the person said he had replaced both the clutch master cylinder and the clutch slave cylinder.
From what you describe I am not sure you have bled it correctly.
I suggest the following:
Depress clutch pedal (person 2 or use a bar to block pedal down)
Open bleed valve, close as soon as pressure goes, ( a pipe into a jar is good to keep area clean)
Release pedal, wait 3 seconds then depress and hold again
Repeat 3 and 4 as necessary untill you have a decent pedal.
This method moves any air bubbles through the system. If this does not work then get it bled using a pressure bleeder.