I was plagued for years with baling out the rear footwell, I've baled quarts at a time and searched for the source for years to no avail.

When I first started with mercedesshop, I got the answer. I cleaned out the drains in the pockets under the hood hinges on both sides, and also there is a drain that allows water inboard where it finds its way into the passenger compartment under the battery just like MBJoe said, but ALSO another one under the master cylinder.

If you will be dilligent in finding and cleaning out these drains, I feel quite confident you will cure your problem.

The rear window seal is a real bear to replace, I would not replace it unless you determine FOR SURE that this is the source of your leak. I've never had any problems with rear window seals. Psfred has been a little less lucky than myself it sounds like.

Definitely clean out the drains with wire before replacing the rear window seal. Cleaning out the drains costs nothing. I don't want to even think about what it will cost to replace the window seal.

Good luck,