Rear brake lines have rusted out causing a safety concern. Mercedes will not extend the warranty to repair the recognized inferior parts as they did for the rear subframe. The rusty rear brake lines are related to the rusted subframe which was repaired under extended warranty by Mercedes at no cost. The same should apply to the rear brake lines. I am currently having the rear brake lines replaced due to this rust and safety issue. Please require Mercedes to extend the warranty and related repair to the rear brake lines as it is systemic to these cars.