The bleeder pulls fluid out the caliper bleeder nipple to the vacuum tank , and the master cylinder level will drop. I have tried bleeding all 4 brake calipers.Testing the pedal it has no resistance,easily goes to floor. 3 times I have used the vac system . I have Re-read all instructions,made sure of correct air pressure . Lost on how to proceed further to get a firm pedal. Any help appreciated.Thanks.