I have 2003 Mercury Sable that leaks water onto the right front floorboard and into the blower motor every time it rains. i took it to the dealership and they said there is a Technical service Bulletin(TSB) for this problem. I went to the service department and talked to the service manager and he showed me a list of parts along with the detailed procedure to fix the leak. I installed everything I was supposed to and did exactly like the repair procedure said. The car still leaks when it rains. Is there something the dealership isn’t telling me so I will have to take it to them to fix?
The problem could be coming from the passenger side door. Open the door and check the lower edge of the door for the openings. These are small square holes that allow water to drain. If they get plugged up, water can come down the window, into the door and out onto the floor.
Another place could be from under the cowl. With the hood up, the plastic cover between the firewall and the windshield is the cowl. Remove it and you should see something that looks like a short smoke stack. It should be sealed around the bottom. If it is sealed and water is getting over the top, then the drains that go down behind the fenders, just forward of the door, must be clogged up.