Extending the car cylinder – How?

Hello, I would like or have to expand tomorrow the outside clutch sensor cylinder on my V70 (1997, petrol, switch) because I have the assumption that it is broken (severe heavy-duty circuit especially in the first and reverse gear and that despite new clutch and transmission oil). When changing the clutch recently he did not go out (probably after 23 years connected with the holder) and left it in it or he left a lot in his individual parts which allowed me to release the gearbox. Is the reason why the clutch is not always cleanly separated because the piston no longer has the entire stroke and pressure … !? But since it is now replaced by a new one you can now also go there with greater powers and more ruthlessly. Vlls with a hearty blow with a heavy hammer? Or does someone have a better idea, experience …? Thank me for your helpful contributions in advance!