Nasty surprise when removing the old carpet
 

I found this when removing the carpet to put in my new interior. It's pretty nasty, but seems to only be along the seam where the floor pan meets the body, forward of the door to parallel with the pedal cluster. I know there are a lot of "rust repair" threads on the forum, a couple of which are running concurrently with my post, but what would be the most accepted method of repair for this problem specifically? Thanks for ANY advice, I wouldn't even want to own this car without this group! http://forums.pelicanparts.com/uploa...1285626377.jpg
http://forums.pelicanparts.com/uploa...1285626420.jpg
http://forums.pelicanparts.com/uploa...1285626464.jpg

Does anyone have any suggestions? Weld in patches? Whole new floor pan? I don't even know where to begin here, guys.

Carefully check over the rest of your floors (use an ice pick), especially near the foot wells. If that's all there is then I would just weld in a patch. Since it is a 74 chassis I would look over all the typical problem areas on the car, rockers, bottom windshield corners, front bumper shock support, etc.

I would clean the area up on both sides in & outside see how much more you find, if that is all, I would patch it with something like 18 gauge steel mig weld it in coat it with something like Por-15 (might as well clean & strip the entire interior floor while at it) add undercoating after on the out side and call it done!!

Regards

Have you had a good look around the rest of the car? It's possible that you have or had a leak around the windshield at some point and if you have or had a rubberized backing on the mat, there is no where for the water to go.Two ways of proceeding as I see it, full exploration and paying ($) for the consequences or doing micro exploration and removal of the unsound material in the area that you've already uncovered and patch the areas that need it. How do you use/store it? You're in Texas, I'm thinking that if you garage her and it's a nice weekend car, patching will last almost indefinitely.... if prepped and finished properly IMHO. Cheers and good luck.

There is a little bright side: At least it's not in an area that will require a paint match like on the exterior of the car.

Did you clean up the area before you took the pictures? If not, that looks like old rust that has been there awhile as opposed to ongoing rust as I see no flakes or dirt around the rust. Either way you are going to have to find the extent of the rust and then cut and patch.

+1 on windshield leak, check the lower corners of the windshield carefully, if you get a leak at that point it goes right down to the floor.

First thing to do is find the source, as mentioned. Then find any more rust. After that, determine how structural that is (I don't think it's all that structural). Maybe treat it and leave it. If you repair it poorly, it will devalue the car more than if you arrest the rust process and monitor the area.

I would want to what is happening on the outside before I decided on my next move. Generally speaking, if you don't drive in the rain you have a fair amount of time to deal with this, as in at your convenience.

Simple repairs would start with POR 15 and epoxy putty, making sure exterior holes are plugged. Very few here would advocate that, but it can be effective in preservation, and is something one can do for very little money with very little experience. Plating welded steel over rust is a no, no, so generally welded repairs involve cutting back in layers to expose the inner rust, and welding in steel from the inside out .

You do want to look in the front trunk, and examine the whole underside. However, that looks pretty minor on the general scale, and sometimes a car will have one or two little spots like that while the rest of the car remains sound.

Uh, what he said. SmileWavy

Cut it all out like the cancer it is. Do not "treat it and leave it". Eradicate it completely. Kill it. Without mercy or remorse.

Thanks everyone for all the advice. I am pretty sure it was indeed caused by a combination of a leak from the windshield and moisture trapping floor mats, and happened well before I ever took ownership of the car. The passenger side floor pan is perfectly fine. All the suspension points are solid.<p> It looks like I'll be having that part of the floor pan cut out and patched. Time to find a good welder here in town...