The camshaft adjuster solenoid (which is related to the variable valve timing system) may fail or timing chain/balance shaft components may wear, resulting in illumination of the Check Engine Light and various drivability issues. Mercedes-Benz has released a service bulletin outlining specific repair instructions depending on fault codes stored.
Resources for the Repair and Maintenance of your 2009 Mercedes-Benz CLK550
2009 Mercedes-Benz CLK550
2009 Mercedes-Benz CLK550 Problems
Going over large bumps in convertible models may cause the roll bar to deploy, rendering the roof inoperative. Special tools are generally required to return the roll bar to its stowed position.
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.
Computer control modules for the seats and doors, the CD changer, and the brake lamp switch tend to fail.
The engine may develop a stalling and/or no start condition due to a failed crankshaft position sensor.