just bought a 2006 s4 cabriolet with 23k miles. Every time i come to a full stop the brakes produce a loud grunt and low clanking sound. The grunt also happens when i release the brake. Anyone experience the same problem and have any ideas why this may be happening.

 

Not experiencing it myself, but if it were happening to me I'd be thinking a bolt or two is missing from the caliper, and it's moving a little. The other option is that you're out of fluid - or so low pressure isn't being distributed properly. I'd take it to a dealer if under warranty, or at least a brakes plus for a cursory look and repair. Brake system shouldn't be making any noise at all.