water leaking into trunk/bottom of rear window

Is it a convertible?

Could it be leaking in around the tail light area?

20001 mustang:

Water may be leaking in around the spoiler bolts. There are supposed to be "squishy" washers or gaskets that will create a waterproof seal but, if the previous owner had removed the spoiler (some people do), then look for drips there. The spare tire well is the low point so water will always end up there.

You can get new squishy washers from your Ford dealer or you could use RTV. Do not overtighten the nuts because you can pull the studs out of the spoiler. Snug, not "Arnold tight".

HTH,

Chris

When it comes to water getting into the trunk area, it's not going to be a quick find/resolution. I have a zx2 that had water getting into the trunk. It wasn't coming in just one area. Water is tricky that way. I replaced the old trunk gasket, and I had replaced all the "squishy washers" everywhere there was one for the tail lights, spoiler, etc...The PITA leak was a hairline crack at the welded body seam ( where the rear quarter panel and trunk are put together, both sides behind each tail light). I used clear sealant in the area inside and out, and no more leaks.

Instead of using dyes to find where water is coming in, I read a trick to help find water leaks, by using flower and then hosing the car down. The flower gets picked up by the water and brought into the car and leave a visible trail.

Ended up driving around with the interior of the trunk all pulled back and the plastic parts stayed in the garage for the couple of months because when I thought one leak fixed, I found another place where water was coming in...just this girls' 2cents worth..........Good luck~~~

I'm not sure exactly what you're saying but there's a gap between the rear window and the trunk lid and there's a gap between the rear fenders and the trunk lid too. Water should come off window and run down through that gap into a channel under the lid, around the sides and exit under the taillights. Maybe that water is getting past the trunk seal. Leaves and crap can collect in there and block it up and if leaves or something is holding moisture, it makes corrosion much more likely so there could be rust through there too. It could just be that the seal just is worn or the trunk lid is not adjusted correctly and not making a good seal.