Yeah....you don't want to ever pump the pedal with the slave cyl removed. The only time we do that is with 2 people.....one person under the car who first loosens the bleeder screw and once it's loose, the other person slowly pushes down on the pedal. At that point, you're not trying to create any pressure.....you're just pushing the pedal enough to push fluid thru the bleeder screw. We do the entire bleed process with the slave cyl hanging loose below the car. Pumping the oil can to reverse bleed from the slave up to the MC....as well as bleeding by pumping the clutch pedal......none of it puts any pressure on the slave cylinder as the only time we push down on the pedal is slowly with the bleeder screw already opened before we begin pushing.