One problem related to timing tensioner has been reported for the 2003 Mercedes Benz C230. The most recently reported issues are listed below.
At 178,000 miles the timing chain tensioner failed while the car driving approximately 25 mph and allowed the timing chain to skip several teeth leaving the car stranded and potentially causing thousands of dollars worth of damage to the engine internals. The car was dealer serviced since new and always had maintenance on time. There is thousands of people online that have had the exact same issue and Mercedes Benz USA refuses to do anything about it yet they acknowledge they made them wrong because they have updated the chains and tensioners.