I have eight years old Caroma Uniset cisterns which don't know when to stop taking water in.
After flushing, they start refiling the cistern all right, but then the last 2 - 3 liters come in very slowly, just "hissing" in, and the mechanism doen't stop at any point. If I turn the tap off, it's all good.
The likely suspect is the grey cylinder on the right. Parts probably requiring replacement, but which ones to start with, please?