Was informed about the extended warranty for the rusting rear sub-frame issues on this make and year. Upon speaking with the dealership and further research online the rear hard brake lines are rusted as well and not covered by Mercedes. Upon further research this a common issue and danager to my safety and others as well. Upon work required to fix rear sub-frame would make it easier job to also replace rusted brakes lines. But Mercedes ds not cover that and wants to charge customers a extra 3500$ to fix something that should not be happen as well. With the sub-frame out for replacement would make sense to replace other rusted parts with the extended warranty. It’s a major safety issues already with rusted sub-frame and also added rusted brakes lines. This should be investigated further into to keep everyone safe. There are lot of owners unaware of this issues that could lead to brake failure. We use our brakes to stop and most new cars should not be having this issue so early.