Clutch Sinks to Floor and Does not Return

Clutch pedal sinks to floor and has no pressure to return to its normal postion. Has anyone had a similar problem? What should be done? Any clues appreciated. TIA.

PS. The mechanic suggests changing clutch slate and master. The hydralic part has slow internal leak and needs to be changed. The clutch and transmission have alreadt been already changed.

either slave, master, or both will cause it. your mechanic is right.