Sunroof seals. Had same issue but I sealed the sunroof with silicon until I can find the replacement seals and felt (the felts NLA). No issue since. major rains and dry as a bone. Before this, I had 2 inches of standing water in there after a rain!!

The sunroof is intended to leak. There is a catch pan that is supposed to drain out in 4 places (behind the front tires, and at the trim where the c-pillar meets the rear fender). If your drains are clogged then the pan fills up and floods the interior.

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The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

see pic and arrow.

i tore the interior out completely. water collects right at the back of the driver's side rear floor pan. i cannot figure out where it's coming from for the life of me.

trunk is dry. front floor pan and pathway back to that spot is dry.it's not coming down any of the wires.

any further thoughts?

it may be time to peek under the headliner.

Attached Thumbnails

 

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car