rattling noises
 

have 98 c280 79k miles, just recently hearing rattling noise coming from underneath car. It is unpredictable, sometimes wont hear it all day while driving, other times hear it intermittenlty while driving, sometimes hear it while in park, just comes and goes and has a mind of it's own. Anybody no what it could be?

I would check the exhaust system. Look for a loose exhaust shield or component that is allowing it to rattle.

Cat converter. Get a rubber mallet and get under there (not running) and tap on it with the rubber mallet. You will know when you find the trouble. The guts come loose inside. Don't replace it with Catco!

is there a passenger side cat and a drivers side cat that if I find the side the rattling is coming from, would I only need to replace that side?

Well I don't have the C280 so I can't say, but I think they are always one piece, whether they have two cats or one. It is a long assembly, about 4 feet long. You can get aftermarket ones. As I recall they are around 350. But don't get the Catco one. A V8 might have two seperate ones.