2004 A6 S-Line quattro. Ok, I have about 15k miles on this set of pads and rotors, and got about 30k out of my last set, so I don't want to go ahead and do a whole brake job yet. So, just recently I started hearing a slight "click" when braking. It is just one click and doesn't do it every time. Seems if I brake hard, it won't do it again for a couple braking times. Anyway, I am thinking it is a pad that has come loose from the metal backing. I will call the shop that did the job last time but honestly, it is such a pain to take it to them and they always take too long to repair stuff. So, I would like to try to fix it myself. IF it actually is a pad that has come loose from the metal backing, is that fixable? I have found some info on the net about a brake pad adhesive but can't seem to find the actual product. Should I just go ahead and replace the pads on the side that has the issue?

Thanks for any info.

BTW, anyone have any idea where I can get an electronic copy of the service manual?