Join Date: Jan 2019
Location: Sedgwick, Kansas
Rivets and adhesive will typically form a good place for water and dirt to collect, and get a really good case of rust started. Structurally, it works; they wouldn't come loose or anything. But for longevity, you'd be a lot better off welding it up right.
Another option if your floor is structurally sound but just has lots of little holes, (and this will surely make some people scream!) is to clean up the rust using something like phosphoric acid, put down a coat of POR-15, and while it's wet, put down some fiberglass or carbon fiber mat. After a couple more coats of POR-15, it becomes 'POR fiberglass' more or less. Under the car, you'll want to clean up as well, and coat the other side with POR-15 and undercoating to make sure that water can't get back in that way either.
Do NOT use regular fiberglass resin for this fix. Nomal fiberglass doesn't have much 'stretch' to it, and because it expands and contracts at a different rate from metal. It will soon come loose and cause problems, allowing moisture back in, and trapping it. POR-15 has a lot more adhesion, and while it's very tough and strong, it does offer just a tiny bit of flexibility, so it expands and contracts with the metal it's stuck to.
You don't have to make the surface smooth, as POR-15 hangs onto a rough surface much better anyway.
As someone with no welding skills or equipment, and being dirt poor, I felt like this was a better option than paying someone else to do a repair that I might not be happy with anyway. While not claiming that this is a perfect factory fix, it's certainly as good or better than many of the hack jobs I've seen where someone cut out the floor and welded new stuff in badly.
I did this to my Cougar, and so far, I'm really happy with how it turned out. If, later on, I discover that my repair was a bad idea, I'm still back to where I was before: I need to cut out my floor pans and put new ones in. From the outside, it's perfect and looks factory stock. Under my carpet, it looks shiny and black. I don't think anyone's going to care except me, ever, and I don't intend to sell the car.
Last edited by Grimbrand; Today at 05:54 PM.