2002 Chevy Silverado Clutch Throwout Bearing Making Noise

Just purchased this Chevy truck with clutch problems. Clutch does not slip at all but the throwout bearing is making a clak-clak-clak sound that matches the engine speed. Someone suggested that it might be a bad slave cylinder or that the hydraulic system may simply have air in it. I stuck my head under the truck to look for a bleeder valve on the slave cylinder, but the hydraulic line runs through a 1-inch hole in the side of the bellhousing and there doesn't appear to be an accessible bleeder valve. How do I bleed this system???