The sway bar end link joints may wear and cause a knocking noise over bumps. Loose or warn links should be replaced to correct this type of noise.
Car Problem Reports
Mercedes-Benz C230 Worn Sway Bar Link Joints Causing Knocking Over Bumps
Mercedes-Benz C230 Problem
Average Mileage: 91,000 mi (82,000 mi - 100,000 mi)