Date registered: Dec 2012
Vehicle: '02 E430 4Matic, '14 MB E350 Sport 4Matic, '01 BMW 740i, '16 Golf R, '17 Audi Q7, '10 Chevy Suburban
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Quoted: 30 Post(s)
Have you checked the drain ports in the sunroof carriage area for blockages? You can pour water to see if it drains. If not, use string trimmer line or something similar to "snake" on the ports and drains to clear it.. or even compressed air.
I don't know he hose configuration on the W210's, but on My BMW the hose behind the headliner actually became detached and caused a similar leak.
Run the car with the AC compressor / windows closed on to dehumidify the interior. If you can't get it resolved before the next rain, tape up the sunroof to keep the inside dry.