Toyota Repair: brakes, oil leaks, oem pads

Question
I have A 97 4runner 2wd. I recently replaced the front brakes. I just replaced the pads, no resurfacing of the disc. Now when I back up i hear a popping noise when i apply the brakes. I have removed the pads on both sides to recheck them and no sign of anything. I was wondering if some damage may have occured while pushing back the pistons. No signs of oil leaks. Any Ideas? Thank You

Answer
Possibly brake pad movent in the caliper especially if the replacement pads were non factory pads, make sure that the shims and the antirattle springs are installed and try using OEM pads with all the required hardware if the problem can't be resolved.