Frankly there are no problem motors for GLK. But you should not count on an absolutely cloudless existence. At the pre-styling crossovers GLK 220 CDI, all the fuel injectors are changed and the electronic engine control unit is reflashed. However, do not rush to be frightened of such a significant procedure. This difficult operation has the status of a service campaign and is free for the owner of the car. Alas, the replacement is not always called, but if you visit the dealer of your own free will, as a rule, do not refuse.