Knocking noise rattling like marbles on the right front, apx 6-8 " from bumper ?

What is your question?

Noise occurs when in motion. A knocking noise rattleing like marbles on the right front , about 6-8 " from the bumper. It sounds like there is something inside a black cover that seemingly protects the engine in this area. My mechanic is uncertain about it , as are the other Mechanics he has consulted with. Hoping you can help !!!!

How long has your 2002 Mercedes-Benz C240 had this problem?

a few days before towing the vehichle to my mechanic who has had it going on one month while researching.