Water is leaking into the car

Depending on what you have and where it's coming from, it's generally caused by a leaking sunroof seal or door seals, most commonly the sunroof. The first place to check if you have a sunroof is to make sure the leak is not starting there; check the seal closely with a good flashlight and see if it looks worn externally; if it is, then open the sunroof and see if there's any evidence of the leak there. If you see a leak there, you usually have to replace the seals in the sunroof section and rebuild it to fix the leak or install a sunroof delete*. To find the P/N for your MB, we need to know your model year and potentially the chassis code if it's a rollover year, such as the W203-W204 transition.

IMOPRTANT: *If the car throws an error about the sunroof with a sunroof delete, you will need to code it out of the car with a bidirectional scan tool or the MB STAR software depending on how the car handles feature coding unless it can be done with an all system scanner lacking this. It generally requires bidirectional support.

If the sunroof is good, check the door seals and look for evidence of damage or even a loose seal. If the seals are loose, you will need to remove them from the car and reseat them unless the area can be reseated without taking the entire seal off.