l got a 2003 lincoln town car and when it rains there is a huge wet spot that forms in the backseat carpet on the passenger side. It was like that couple weeks ago and it rained during that time too. Its not a little leak either it is soaking in that area. l was wondering were the leak would have come from. Thanks
Yes it does have a sunroof

Does it have a sunroof?

easiest way of checking this, take your garden hose and hose down the car, then look where the water is entering the car

l would check the back window gasket and the trunk seal. Its pretty much got to be one or the other.

probably from the seal around the door or sunroof if you have one. there is something not right about it.

you can have someone sit on the inside of the car and spray the car with a hose so he/she can see where the water is coming in. Then try to see if you can fix it yourself, or you can just take it to a garage.

l do not know how to fix seals and gaskets, but l do not imagine it to be too hard if you're knowledgeable about cars.

Good guesses, but it is not the sunroof, nor any of the previous .

The leak is coming from the front, & the first place people usually see it is in the right rear floor board.

If u pull the carpet back in the right front, u will find that it is wet under there, too.

Leak is from the cowl. Take the passenger cowl panel (black plastic piece at the bottom of the windshield) off. Under it, u will see a sort of oval-shaped plastic piece, with a screen on top of it. That is the fresh air inlet for the Heater & A/C. The gasket that seals it to the firewall has failed. Remove it.it is two nuts. 11mm, if memory serves.
Clean off the old gasket & reseal it. You can get some thick gasket material at Lowes or Home Depot that will do the job, or u could even use a thick bead of silicone. Be sure to clean the surface it mounts to, also.
( l actually use 3/8'' 3M Ribbon Seal, which is butyl rubber for installing windows, but works great for this..you can get it at serious auto parts store, but not places like Autozone or Pep Boys)

Also, clean all the excess leaves & tree debris from around the housing.

That will fix it.

I've probably fixed over a hundred of these with the exact same problem, & maybe one of them was not caused by this.