I did a front brake job on my '03 a few weeks ago, and had bought pads and rotors, planning to not replace the calipers. But then a bad caliper piston showed up, and I didn't want to mess around with rebuilding it, so I went to Autozone and picked up a Duralast reman caliper. Turns out the washers that were included with the caliper were just slightly too large. The difference in size was very little, but the new washers were just large enough to not be able to drop into the recess of the caliper brake line fitting. I figured that reusing the old ones would probably be ok, and with no leaks, that appears to be true.
I know for certain that those replacement washers would have leaked. So could this also have happened to you? Did you compare the old washers to the new ones?