Most of it seemed like surface rust, but this one in particular is really thin and looks like cottage cheese. No wonder they had a plywood piece fitted underneath the carpet.


Time to pull the welder out! Any hints and tips?

Do you guys use underlayment? It seems like all the rust really came from moisture trapped underneath the existing one. I'm already going to put RaamMat Audio (like Fatmat, only butyl based instead of asphalt) sound deadening throughout the floor, but if the $70 of underlayment is just going to trap more moisture and add weight, then maybe I should do without it?

 

congrats, you officially own a mustang!

the car probably had a leak in the window that kept the carpet wet. it doesn't take much water over 40 years to cause rusting. as long as you fix the leak you'll be fine to put in whatever underlayment you want to use.

 

For tips on rust repair, check out "A woman's project: '68 Mustang". Here on the forum. Should pretty much cover what your going to do and how to do a good job.

Also I found the "FAQ" was very helpful as well.

Post pictures of your work as you go, I'd love to see it progress.

 

check if the cowl is still good. no point in repairing floorpans if that is still leaking

 

Good luck keeping floor dry if you spend any time in the rain or wash your car.

I have tried different things on the floor boards.

My 64.5 floor is painted and my 67 is undercoated. I prefer the paint. Should recheck floor every 5 years or so.

It is a royal pain to remove some types of undercoating if water finds its way underneath.

It is easy to touch up painted floors.

The cowl repair kit Kali mentioned is pretty simple to install and is a must if yours leaks.

 

I couldn't find this owner or post. Is it still available?


The major rust is in the rear passenger seat. Could a leak from the cowl make it's way there? Or is it more likely a leak from one of the rear windows?
Would brushing on Por15 help protect the metal on the inside? Or will standing water make it's way through anything? I'm going to grind away and treat the rust this holiday weekend. Will post more pics soon

 

Here you go : https://mustangforums.com/forum/clas...-fastback.html

 

I would not waste money on Por-15.
If you want por-15 then at least spend some time googling the pros and cons.

For floors I prefer:

clean to bare metal.
keep all good OEM metal, replace bad.
acid etch then rinse.
epoxy primer.
top coat w/ decent paint.

 

plywood and sheet metal patches are very common on these cars.

You'd probably be surprised what you would see under the carpet of alot of great looking so called "restored) stangs out there.

 

I would also bet that the floor underneith the seatriser is swissy cheese also. Be sure to check it from the bottom. I would replace that entire section if you want it done right and are planning to keep the car.