The hydro boost does give a sense of a spongy brake, its best not to have the engine running and to pump down the pedal so you have no boost at all when bleeding the brakes, then when you get a hard pedal you know you do indeed have the air out.. with the 4 wheel disk brakes you should not be able to push the pedal down more than an inch or so before it stops.. Years ago i had an old Datsun 510 that i did a master cylinder in, but at the same time added a power brake booster out of a 240Z.. after bleeding the pedal would only drop a 1/2 inch with you foot.. start the motor and i could push the pedal right to the floor with your hand.. it was like driving the school bus i had with air brakes, 4 years later i brought the car in to have a safety check done, and the mechanic came to me after and commented on how well the car stopped..