Pinch weld rear quarter window leak

[scenarioL113]

After my 1986 Mustang SVO was painted I had noticed that after I rinsed it, I had water on the floorpan rear seat area. I spent a good amount of time and "thought" the quarter glass was the culprit but finally realized the problem is the pinch weld. Water is entering at the pinch weld on both sides of the car. The driver side is worse (it had the quarter panel replaced many many moons ago and not a great job).
It leaks when water is directed at the quarter window, runs down the glass and catches the lip of the pinch weld and enters there.

Luckily I noticed this since the interior was out.

I used silicone to seal it better and it is OK, especially since the car is garaged and not driven in the rain. I do want to fix this better and correctly though.

Just looking for suggestions...

I was thinking panel adhesive possibly to fill the small gaps and then seam sealer???

I dont know really what the best way to handle it is. I only want to do it once bc the triangle moldings are not the easiest to deal with and dont want to scratch the paint removing/installing them. I want it to be the last time those molding get removed

[KevinK]

Not sure exactly what area you are seeing the gap. Seam sealer was made to fill in gaps and holes as well as water proof areas. Probably up to about 1".
Anything silicone was likely not used at the factory as it can contaminate paint surfaces during production. I would just get some 3M seam sealer in a caulking tube.Any hardware penetrations would be sealed with 3M rope caulk. If you have a flapping panel, then reinforce it and use some panel bond.

I'm sure a body professional might have a different suggestion. The above is more DYI.

[scenarioL113]

[gr79]

Could try a bead of black RTV first or reseat the glass in urethane or something. Has to be just so.
Seam sealer nah not there. Butyl tape works but attracts dirt and would likely show.
Whatever allows the trim to reseat correctly.

[scenarioL113]

Thanks for the replies so far.

The glass itself is NOT leaking. I had the interior out and ran the hose against the glass. The leak was definitely from the pinch weld.

The pinch weld from when the cars were built I would think had to be sealed with something...I think? Maybe it was just globbed up with that butyl goop. I think there is some kind of weatherstripping foam or something that "pads" the triangle molding against the glass BUT I do NOT think that it has any sealing characteristics.

[gr79]

From what i recall replacing 1/4 glass is that the 1/4 panel pinch weld was behind the glass.
Continuous metal stamping from top of seam behind the glass, then down under the glass, down the side.
Mine was replaced too but the body shop did not use the whole panel prob to save time.
For sure did not replace any metal by the glass.
If the panel was replaced all the way to the door, then it may have been cut outside at the bottom of the glass.
With the glass in place. Glass not removed to butt the new panel further up against the factory pinch weld.
May have to remove the glass to 'reflash' the seam solid under and behind glass like a house roof or something.
Butyl or asphalt house window frame tape may work to form the contours if it can be hidden.
Puzzling both sides leak though if the ps 1/4 panel was not replaced too.

Maybe water is intended to drain down the inside to the rocker and out like a door.
I use black plastic roof cement to seal rear wheel well rust repair patching where the finish does not have to be smooth.
Thinkin remove the inside 1/4 panel trim and get some up in there at the seam from the inside with a stick.
Works like thick seam sealer next level up. Slowly hardens no cracking, cheap and much messier to work with.

[wraithracing]

It sounds like the quarter panel was a patch job and not a full replacement most likely and they didn't do a good job of resealing everything. The quarter window is normally sealed with butyl tape and held in place with the metal clips with the fuzzy material on against the glass.

In my opinion the best and most likely permanent solution to this issue is to remove the interior quarter panel trim and verify exactly where the water is able to enter the vehicle interior and then seal as needed. It could be the pinch weld as you suspect, but it could also be at the pinch weld around the glass and the butyl sealant. Depending on where the leak is and what the area in question truly looks like you may want to use a urethane structural adhesive to seal and strengthen the pinchweld area. A good automotive grade seam seal either in a caulking tube or even the brush on type may work well too again depending on what you need. You may also consider using urethane window weld for the glass sealant as it is much stronger and will seal much better than the original butyl tape. A little less forgiving to work with, but quality stuff that will seal well also. Good luck!