I think it has something to do with the pads. My car doesn't have that noise 'til recently when I have my pads changed(and I have the same situation as you have. Noise only heard when light braking). My guess is that MB uses Metallic Pads, which produces more noise then normal pad.
<LI>1992 Mercedes-Benz 400SE
<LI>Pearl Grey/Black Leather
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