I fought the same problem for two years before giving in and taking my 2004 Lincoln Towncar to the dealer. They knew exactly what it was, it was the vent cover or cowling under the hood as answer #2 described. It was letting gallons of water in and I had to replace the carpet. The dealership repaired the leak for $192.00, end of problem. I am so thankful to have the problem repaired but my feeling is that this is a defect and the dealership should have repaired it for free.