I had that trouble after changing the brake pads of my Lexus LS400, sound was coming out of the pads that tears your ear and specially in traffic jams where you use the brake more....
i went to garages that told me to polish the disc brake others told me to change the pads for original because they were not sure that the pads I already installed were original, but no matter what the sound still coming out so I've decided to change the disc brake for a new one ... that's what our dealer told me...
NO matter what the sound was still coming so i went for a detailed inspection manual of the brakes and i discovered a missing shim kit that supports the pads installed and maintains stability to the disc.... that one
pepole throw while installing a new pads cause the new pads thiknees in more than the old ones so they throw them cause they don't know how to install them all together..
Finally the sound was bye bye bye.... I ever lived happily again.....
in order to know more about installing the kit follow the link
http://www.clublexus.com/index.php/fileman...81/lbr00295.pdf
download it and take care....
lbr00295.pdf