'90 300e 4matic front (brake) grinding
 

Recently, there has been a distinct metalic noise which comes from the left front side when the brakes are applied on my 300e 4matic. As the car slows to a stop this noise becomes more grinding in nature, as if the pads are totally worn to the metal. I checked the pads, which I've recently replaced and while they have plenty of pad material on them, I noticed 3 small areas where material appeared to be black and gritty. I also noticed that the rotor surface appeared slightly elivated/depressed, possibly related to the distorted areas on the pad. Might the pads be causing this problem? Or is it possible that the brake loading of the left front is causing a wheel bearing to make this noise? Thanks; Dave

The rotors may be worn to the extent that the raised rim of rust you get around the edge of the shiny bit the pads contact is rubbing on the pad backplate.

What kind of pads are you using, how worn are the discs? I once had a stuck piston that made a grinding noise of sorts.