Drivers side footwell rust - Where is the water coming from?

[Malleus]

Well, I don't work for them, and have no experience with them. I was only offering an observation.

I called them, just to satisfy my own curiosity, and they confirmed the sunroof assembly is NLA.

 

[Irish Reiver]

Is / was the OEM windscreen glass thicker than the typical Chinese safelite replacement glass?

 

[Malleus]

Is / was the OEM windscreen glass thicker than the typical Chinese safelite replacement glass?

No idea about the Chinese glass, but replacement US made glass is dimensionally the same.

 

[alia176]

I didn't read all the stuff up above, but did someone check the sunroof drain hoses to make sure they're clear? There should be two up front, going into the body cavity under the door opening. Two in the rear goes into the rear Q panel area.

second possibility of water ingress is the windshield seal. Check to see if water is getting around the bottom windshield seal, then tracking along behind the dashboard, then eventually onto the floor.

Here's where I saw water in my 80

 

[Kernal]

To find the leak the OP could take a garden hose (without a nozzle) and hold it over one section of the windshield at a time to find the leak ie: right lower, right upper, center lower, center upper, etc, etc. Then do the same with the sunroof, left side, right side, front, rear. Using a bright flashlight and with the front kickpanels removed (and standing on your head in the footwells looking up under the dash) you'll find the leak eventually.

Regarding the sunroof gasket; as mentioned above it's not available as a separate part, my guess is because it would have to be a very precise process to attach the rubber to the glass so that it is firmly attached and doesn't roll or get pinched or peel off the glass.

FWIW years ago I contacted a manufacturer of custom rubber gaskets and they said they could probably replicate the gasket (for a large set-up fee and minimum order). But then the tricky part would be cutting it to the exact length and installing it correctly with the proper adhesive. It could be done but someone would have to lay out thousands of dollars to get the project moving.