I have detailed pictures of what is happening ... it happened to my 99 Cougar, only it was in the truck area and collecting in the spare tire well. I would imaging that the type of problem is related because of the way that the panels of the car are welded together. It's a quick easy fix.
Picture of the path the water takes to leak in:
To fix the problem, peal back the trunk opening weather stripping:
Identify where the gaps are where the metal panels meet:
Apply copious amounts of Black RTV Sealant to these areas and down the entire spine. This will not only seal the areas where water can get through, it will also help adhere the stripping to the spine making a nice impenetrable water barrier.:
Press down the weather stripping:
Notice in the weather stripping that there are small pin-holes in the large upper portion. This is by design to allow the thing to compress without popping. Problem is that sometimes the holes will be on the side and channeling rain water will make it inside the weather stripping. From there, it will take the path of least resistance ... right to the nearest gap in the panels. The technique used above helped me completely eliminate my leak. Give it a try
