Cadillac Repair: 89 Cadillac Seville Brakes, cadillac seville, power brakes

Question
The diagnostics only showed the B120 code. The noise is like a compressor filling and starts when car is started and quits after a few seconds, but then when the pedal is pushed it starts again for a few seconds and then quits as it slightly pushes the pedal back at you. The rear brakes can be bled, but the front don't seem to have any pressure to them and no fluid comes out. The front rotors are free and do have play, so nothing is stuck or jammed in the calipers. I'm stumpped.
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-----Question-----
My 89 Cadillac lost it's power brakes showing brake light and Anti lock light always on. I replaced the master cylinder with a used one and replaced the original ABS system back on to the used master cylinder I replaced the old one with. I have not bleed the lines yet, but now when the brake pedal is pushed it acts the same only you here a brake system noise working and the pedal builds pressure pushing back out some. The noise it makes has me baffled and there still is no power brakes. Is it the ABS system?
-----Answer-----
Describe the noise. And run diagnostics.
On the a/c panel press off and warmer simultaneoudly and write down all codes that are presented.

Answer
Well the noise your hearing is the suspension compressor, the compressor will also stay on for 10 minutes after the ignition is off, if your car needs to be leveled.
As for the brakes, you might want to try filling up your master cylinder with DOT3 fluid, pumping your brakes with the ignition off about 20 times, then fill it up again, pump the brake pedal until the master cylinder is full, and then bleed your brakes in this order. Front right, Rear right, front left and rear left, fill up the master cylinder again and pump the brakes again, fill it up and this should fix the clearance. Some GMs are out of the factory with the clearance so you dont get harsh braking, but personally i filled the clearance in by bleeding the brakes until the caliper piston is out all of the way. id rather have a harsh braking experience than not having enough braking power.