To expand some on Clois and Seagull`s comments .... if your bleeders on the calipers aren`t completely vertical , you can trap an air bubble and it will drive you crazy . On mine , I had to place a 4x4 on the jack and then jack to front of the car way up to get the bleeders completely vertical . Tapping on the master cylinder and the calipers as you bleed them is also a good idea . We did that on hydraulic sysems that had runs of up 100 feet to help get the air out .
Look at how your master cylinder is mounted . On mine , I had to take it off the mount and tilt it at a 45 degree angle to get the bleeder screw at the highest point and then got 3-4 good size air bubbles out of it .
What Clois is talking about is a good tip . If you move the pedal too fast , you get air in the
oil ... and then you have to wait about 12 hours for the air to separate from the
oil . I slowly push the pedal down after all bleeders are closed until it won`t go any further , hold it for about 5 seconds and then very slowly come back up . I do this about 5 to 6 times .... and my pedal is rock hard now .
Good luck.