I have a 1995 E320 wagon. I just removed the driver's floor mat and the factory carpeting that has the dense sound-deadening foam on the back of it. Underneath (to my horror), was a small pool of water, the foam was saturated. I can't figure out where it's coming from. There's no rust anywhere. I looked under the car at the wheelwell, no cracks or holes. I'm guessing a drainhole is plugged. The one at the bottom corner of the windshield is clean though. Any ideas?