 I purchased a new 2010 GLK in April. About 1-1/2 months into owning the car, I heard a popping noise coming from the rear of the vehicle. I took the car into servicing on June 30th and technicians quickly found and acknowledged the noise. It turns out - after taking apart the passenger side rear cargo paneling - that some tack welding on the frame did not take place during car assembly in Germany.  This is causing two metal pieces to rub and pop while driving the vehicle. An MBUSA chassis technician had to visit the dealership's service department to view the problem. It has taken MBUSA until July 10th to offer a possible repair solution and they still aren't confident this will work 100%. 