If it's not my W210 causing
problems, it's my W124.
I've only just got it back on the road, the other week the pulley on the tensioner sheared off it's mount and it's only been today that I've been able to fully re-assemble everything and get it going.
On it's first post-repair road test, I noticed that there were some drips of water coming from the plastic trim that surrounds the driver & passenger dome light, the 'fasten seatbelt' warning sign and the sunroof controls.
Could this be a sunroof seal that's going bad, or the seal around the top of the windshield that's on it's way out?