Cadillac Repair: 1997 Eldorado ETC, atmospheric air, r134

Question
G'day
2 questions please:
1/When I purchased the vehicle there was a rumble noise through the car when the brakes were applied but no real pedal pulsation. Changed the front rotors and pads but didn't solve the problem. Car only has 70,000miles. Any idea's?
2/ A diagnostic readout on dash shows low refrigerant causing the ac compressor not to come on. Want to refill but need to get compressor to work so it can suck the R134 into system. Does one jump the compressor terminal directly to battery + or does one have to clear the diagnostic readout then it will start temporarily?
Any input will be greatly appreciated. Thanks

Answer
I would need to drive the car to determine what the noise is.

As to the AC, You need to remove all the atmospheric air from the system and then jumper the relay in order to install the freon. For directives and pictures, E-mail: onlineautohelp@msn.com