The rubber bond in the harmonic balancer can decay, which causes the balancer to move and work its way into the timing chain cover. If the balancer comes into contact with the timing cover while the engine is running, it will fracture and damage the timing case and potentially other surrounding parts. The harmonic balancer should be inspected at every service.
Car Problem Reports
Mercedes-Benz CLK55 AMG Harmonic Balancer May Fail and Damage Timing Cover
Mercedes-Benz CLK55 AMG Problem
Average Mileage: 84,250 mi (78,500 mi - 90,000 mi)