00 A4 Braking Problems

Had not had any trouble with brakes till today. Turned the rotors this morning put everything back together the way it was supposed to be, Check to make sure pads were seated correctly, rotors were snug and secure. Put the wheels back on. Pumped the brakes a few times, took it for a test drive. Brakes did fine for about 15 minutes. Then all of the sudden I start hearing this sound as if the brakes are trying to unseat themselves but since there is pressure on them they are reaseating. Its like "ca clunk, ca clunk, ca clunk". Took the wheels back off made sure everything was tight and secure, but still the same thing. Someone suggested it might be the ABS, but i thought that would trigger the indicator. ANY CLUES!!! Thanks

Just so everyone knows, if you have warpped rotors ensure you change your brake pads as well. The pads will warp with them and cause the sound I described. This cured my problem. This is the only car that this has happened.