Slave cylinder.
The only way to answer your question is for you to remove the slave cylinder and take it apart.
If the bore which is 19MM or 3/4" is clean then the Piston seal will have to be bad. But, if the bore is coroded and pitted then I will conclude that moisture is in the sytem and since the lowest point int the system is the slave cylinder that is where it will accumulate.
If the latter is correct, then you must drain the clutch Hydralic system and purge with new fluid. I personally use Dot 5 silicone because it will not abzorb moisture. Where I live in the Great Lakes area the summers have very high humidity, much like Florida. However we also have winter days that are at zero degrees F. That variance allows for the condensation of abzorbed moisture in the fluid to condense and go to the lowest point, the slave cylinder. I started my car last week, it has been 14 years since I have installed a new slave and master and Dot 5 silicone fuild. Dot 5 silicone will not abzorb moisture like Dot 3 and 4 will. So the moisture problem is gone. In your area of high humidity if you use Dot 3 or 4 I would suggest changing it every 2 years to purge out the moisture that is collected from the hot humid air.
TonyK.
Grimsby Ontario Canada
