Do the floorpans have a double layer of material? The top side looks pretty good but the bottom is soft and ate up in places.

Also I did the cowl leak test with water and all the water came out the bottom of the front fender. So are the cowls good?

I do have signs were water has run down the passenger side kick panel, what would cause this leak?

 

floorpans dont have a double layer, the top isnt exposed to elements, remember? theres a very rare chance theres two layers though if the po was a dumbass and did it, inviting rust. sorry, but all signs point to your cowl being gone. thats an extensive repair so be ready. best of luck in ridding your car of cancer.

 

Yeah the idiot that tried to repair my floor pans just threw another layer ontop of the possible original and in some places there are more than just 2 layers. Somehow try to find a drain plug and see if you can seperate two distinct seperate sheets of metal.

 

So even though when I poured the water in the cowl and it did not leak onto the floor the cowls are ate up? Where is the water suppose to go?

 

You would need to pour a lot of water..and slowly. use a garden hose and let it run for about a minute. You want to fill up the pan area around the vent hats and let them soak.

It's possible that your cowl is ok, but your windshield is leaking. Rust can form at the base of the window frame and allow water into the dash area. The corners could be the source of water running down your kick boards.

I would pull the passenger seat out , the glove box, and heater core box out and get in there to do some exploration. With the heater core out, you can reach up into the cowl and feel around...clear debris, etc... for a better inspection.

 

My '71 Grande has double layer floorpans from the factory. Don't know if all year Grande's have this or not, but it does make the interior a little quieter.