I found a rubber plug, about 1" in diameter under the black floor insulation on the drivers side when looking for my water source.

I can't locate the water source yet. I tried to remove this plug to get a look inside, and it fell into the flooring which is about 2 " deep. I tried, but with no success to get the plug back out it just rolled out of reach. I ran the car, did not run the AC/DEF last night, and the floor remained dry. I hope I can replace the plug, does anyone know what that plug is for. While driving, I put my hand over the hole, felt warm air out of it. Do I need to be concerned ?

I'll look further into the water issue this weekend. I think it's AC related.

Sorry I did not post model/yr it's a 1981 280sl euro model. I've kept the car dry all winter and spring too. This should help determine where the water is coming from.

Thanks for the advise.

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1981 280SL Euro 107
1978 VW Convertible
1984 280SE Euro