There are various posts on this, just use the search function (must be logged in). The failure mode is leaked fluid from the slave cylinder. The Root cause of Failure is seizure of the clutch rod thrust bearing which lives inside the slave assembly and is mounted in/on the slave piston. The rotating clutch push rod transmits the rotational forces through the seized bearing and into the piston, causing it to (eventually) spin in the slave cylinder bore, which tears up the bore surface and toasts the fluid seal, then the rest is history. I am trying to get hold of a cylinder to see what can be done (if anything) to maintain the thrust bearing, or employ some strategy to prevent its failure. Hope this helps in your understanding this frustrating design problem. Dennis.