My 2004-registered Mercedes-Benz 320 CDI E Class estate (Elegance) is producing a rattling, knocking sound from somewhere in the front whenever I go over even the smallest of bumps. The car has done 82,000 miles and the local Mercedes-Benz dealership is suggesting that the anti-roll bars need replacing. An independent garage has looked at this and can't seem to find anything wrong with these. While I am happy to have them replaced if that is what is causing the noise, I would be less than happy if the Mercedes-Benz dealer then says it's something else as well, just because they got it wrong in the first place. I would prefer to be informed before I start on the very slippery slope of Mercedes-Benz dealership costs. Based on your knowledge of the model, what could be the likely cause of the knocking that needs to be checked out before replacing the anti-roll bars on the suspension system?