The Clutch master cylinder,may be needing bled or it is faulty.I rather think it has not ben bled properly ,that is if it is newly replaced! You may be able to bleed the system yourself!Loosen the bleeder on the clutch slave cylinder!In stall a length of 3/16 vac line,on the bleeder tip.insert the rubber hose into a container of brake fluid.Top off the brake master cylinder then pump the clutch pedal until the level in the upper cylinder needs refilled,but dont let the fluid get too close to the bottom of the cylinder,or you will fill the line and the slave with air.Close off the bleeder on the clutch slave cylinder.The air should be purged out,and you should have clutch action.If not the master cylinder is faulty.Check for any leaks,looking at the bottom near or on the clutch slave cyl.And even inside the car behind the master cylinder.