Repairing cowl from under dash

The cowl cover keeps water from getting in the cowl, but it does nothing to keep water from coming in the area around the base of the cowl underneath the fender.

You get to cut the car up, park it, or live with it I'm afraid.

Fiberglass is never a good solution. For a quick temporary fix you could try Por15 Epoxy Putty. A more involved - longer lasting fix I did years ago was: form thin galvanized steel (like duct work stuff from the hardware store) into a crown that extends an inch or so beyond the damage. Then cover the mating surfaces with RTV Silicone and a couple of sheet-metal screws to hold it in place. Crude - Yes, but it still doesn't leak and the repair was done 12 years ago.

Just make sure you get the really thin stuff so it's easy to cut with sheetmetal shears and form by hand. Since no cowl chimney repair kits were available back then (and still aren't) for 71-73, making the chimney from available duct shapes was fairly easy. I do remember spraying a coat of krylon on the finished crown prior to attaching it. If it's large, modeling it out of construction paper first might save you some aggravation.

Sorry to hear the fiberglass didn't hold up well--I am one of very few people that actually enjoy working with fiberglass. I'm in a similar situation: My 72 has a leak on the passenger side. I am not aware of cowl repair panels for 71-73's unless earlier ones will work. I don't think mine is badly rusted, just enough to cause a minor leak.

My plan at this point is to cut out the rusted area from underneath, trim it very carefully and as minimally as possible. Then create a new hat from sheet stock I have and use metal bonding adhesive (like Lord Fusor or a 3M bonding adhesive) to glue it in place. After the adhesive sets, the next step would be to epoxy prime as best I can through the stock openings (probably using a brush). The last step would be to insert self leveling seam sealer inside the cowl on the top side. I have a plan (in my head) for clamping it and for making the part, but until I get the dash torn apart, I'm not 100% sure this will work.

I have a welder, but I don't want to weld due to the effect of heat and the resulting seam. The cowl is a structural part of the car and the hat can safely be glued using a proper metal bonding adhesive. An adhesive seals the seam and secures the hat. I have seen the metal bonding adhesives used and tested and the joint is so strong you can actually stretch the metal trying to pull it apart with 10's of thousands of pounds of pulling pressure. Not sure if that would be an option for you, but it seems to make a little bit of sense.

Not to steal the thread--but will an earlier cowl hat work in a 71-73?

69 Rustang said:

Not to steal the thread--but will an earlier cowl hat work in a 71-73?

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I'm not sure which you are referring to. There are two different 65-68 cowl repairs available: The plastic cowl repair kit and the steel replacement panels. You’d most certainly end up discarding (or seriously modifying) most of the steel panel replacement. The key to whether either will work is the inner diameter and the diameter of the out flange. Maybe Chelle or someone can get these measurements for you. As long as the inner diameter is 6” or less, you should be able to make it work. Anything larger than 6” and you’ll have problems mating the heater box to it.

While you’re there, you may want to consider doing what I did, which is attach a screen to the top of the cowl vent to prevent mice from setting up residence in your heater core.

Definitely steel. I have my 69 in pieces, so I can measure that one and get an idea if they will be the same.

If the cowl cover did not work, there is a very good chance water is leaking around your windshield ( the second most common leak on our cars).

CraigMBA said:

The cowl cover keeps water from getting in the cowl, but it does nothing to keep water from coming in the area around the base of the cowl underneath the fender.

You get to cut the car up, park it, or live with it I'm afraid.

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I have a cowl cover and thought that the foam seal wasn't water proof. Mine does not have a rubberized seal. Good for protecting the paint and keeping out leaves and such but not so good with water.

And I'm thinking it'd be real hard for a significant amount of water to make it up through the cowl drain.

If I'm right, maybe she could seal the cowlc cover with something waterproof for a temp/ghetto fix.