Car Analogy

This certainly sounds suspicious. If there is a zipper, isn't that a potential for a leak just like you describe? Either that was a factory seal for this zipper, or it was PO attampt to fix zipper leak that they found. Either way I think this is worth looking at. Maybe try to temp cover the whole window to top joint with duct tape or something, to see if noise goes away. Then you'd know that was it and could look for a long term fix. Only I'd be concerned with dict tape leaving residue on the top or the plastic window. So use caution.

Another thought, maybe zipper came loose, and just needs to be zipped back up? That would explain why noise wasn't there before, and only started recently. Maybe that foam seal was keeping the zipper held and once it was gone zipper eventually vibrated 'down' a little.

Apex1.0

All very good points. That is where I will center my investigation. The Foam I am speaking of was a thin tube/strip that goes across the upper window, on the outside. The part that overlaps the window covers where the foam is. It may be glued to the top, I am not sure, but a piece fell out while I was washing the car. It looked like it was deteriorating.

cdelena

On my '00 there is a thin foam layer bonded to the top in the position you describe but it could not be removed without some destruction to the foam. From what you are describing it sounds more like someone added foam, perhaps after using the zipper to drop the window (not recommended).

Apex1.0

Yes that is it, I believe it tore off. Not the whole thing, just a piece. But it was breaking up.