This is ironic. When I opened the trunk on my newly acquired 85' Mercedes, I too noticed some moisture inside the trunk lid on Thursday morning. It had came a very heavy rain storm on Wednesday night. The trunk seemed very dry however. I could not feel any wet spots. I have not driven it, because I have not had my plates transferred, so the car has been setting. Now what is interesting is that my rear window has condensation on the inside of it. It was sunny that next day, then cold again that night. I have not noticed any "musty" smells inside of the car and there appears to be no leaks inside of it (passenger cabin). Could that just be where it is air tight and the temperature change caused it, or is it likely that my trunk is leaking somewhere. I have been reading things like sunroof drains, taillamp gaskets, fuel filler door drains, etc. I am thinking perhaps sunroof drains. It looks to be sealed good. How could water drip down in there? Where are the drain outlet for those at? These cars are totally new to me.

Thanks!