Cowl vent leak

6Stang7 · Sep 14, 2009

It rained today and I have found out that my car leaks, fairly badly, from the cowl (there was a nice puddle on the driver side floor board). The car is pretty much complete, only needing trim and some parking lights to finish up.

My question is, does anyone have a method to fix the cowl/prevent water from leaking in through the rust holes without having to remove the cowl?

If not, how do you remove the cowl? I know the fenders need to come off, but at that point is the rest bolts, or are there spot welds that would need to be drilled out? The car is painted, so I would like to minimize any cutting I have to do.

My "if all else fails" plan is to remove the cowl vents by having sheet metal formed to give a nice shaved look, weld them in and grind it smooth, then re-paint the cowl. What would I lose by blocking the cowl air vents? It'd like to avoid this, but I'm thinking it might be the best option.

GNGREN · Sep 14, 2009

Depending on how bad they are rusted you may be able to get away with installing the plastic cowl hats.

If that doesn't work you could get one of the plastic covers that clips into the vents from the outside for when it is raining. Down side to that is no fresh air for the defroster. This would also be the case if you closed the vents with a panel.

The correct way is to pop the windshield, drill out 150 or so spot welds, weld in new panels, then reattach the cowl. Not fun but never need to worry about it again. I am working on this on my 67 as soon as I get some more free time.

68Blue302Coupe · Sep 14, 2009

If you haven't already done so, double check that it is actually the cowl that is leaking. The first time I replaced my windshield gasket I did not seal it properly and it leaked pretty badly. I thought it was the cowl, but turned out the cowl was fine. I put one of those exterior cowl covers on to prevent any further rust, although this blocks air from entering the under-dash ducts (easily removed on non-rainy days). I also read about leaking possibly caused by clogged drains on the sides of the cowl. They are only accessible by removing the fenders and can clog over time from leavs, debris, etc.

2+2GT · Sep 14, 2009

6Stang7 said:
If not, how do you remove the cowl? I know the fenders need to come off, but at that point is the rest bolts, or are there spot welds that would need to be drilled out? The car is painted, so I would like to minimize any cutting I have to do.

You may only need to install plastic standpipes, available from ant Mustang dealer, and install them, which takes only a few hours. As for cowl repair:

Mustang Shelby cowl repair

chris66dad · Sep 14, 2009

Here is an alternative repair we did if the leaks are not bad. You can also extend the cuts and replace the tophats if you need to.
This method might be a good option since you have good paint. You will be able to clearly see what it is you will need to do and develop a plan.

CLICK HERE ==> Cowl Repair

Good Luck and BE Safe
Ron

hungrymonkey · Sep 14, 2009

remove the inner fender splash guard(cannot remember the official name)

Make sure that this hole is not plugged with leaves, pine needles, mouse nests... Or a big glob of factory sealant.

If you can get it to drain, It might not leak as bad, or leak at all.

You can access them without pulling the fender.

tx65coupe · Sep 14, 2009

I have one of those plastic covers that I use whenever my car has to be in the rain or is parked under trees for more than a little while to keep debris out. They do defintely serve the purpose. The picture that GNGRN posted is the one I have now. Its the best one I have seen.

It could also be leaking through the wiper shaft holes. Just a thought. The windshield could also be leaking which was already mentioned.

6Stang7 · Sep 14, 2009

I did a cowl test and poured water down each side of the cowl and looked under the dash to see where the water was coming from. On the passenger side it flows down the back of the heater box. On the driver side it comes through the seal for the fresh air tower.
I'm thinking that if I make sure that the run off drains are not blocked, that I can seal the holes up with AB foam or maybe the plastic replacement towers.

68stang351 · Sep 14, 2009

GNGREN said:

^ I have one of these.

I know it's not the right fix, but it works for a poor guy like me.

GNGREN · Sep 15, 2009

68stang351 said:
^ I have one of these.

I know it's not the right fix, but it works for a poor guy like me.

I have one at the moment also. Unfortunately I tried the cowl hats but mine was to far gone. Then when I started to do my T5 swap I punched a hole in the cowl trying to clearance for the Mustang Steve style cable setup. I am working on doing the cowl replacement. I am hoping to not damage the paint too much when I get around to re-welding it all back on. I may need to invest in some 3m welding paper for protecting the paint? Either way it should have been done before it was painted. I even worned the guy that I sold it too years ago and bought it back from a year or so ago. He didn't listen....

6Stang7 · Sep 15, 2009

When I look under the dash, am I seeing the bottom part of the cowl; the part where the waters runs down? If so, it looks like the area right around the fresh air towers is what is leaking, so I might be able to repair it without removing the cowl.

GNGREN said:
Then when I started to do my T5 swap I punched a hole in the cowl trying to clearance for the Mustang Steve style cable setup

I have have the same issue pretty much. I made my own cable clutch conversion when I installed a T-5 and I had to "massage" the bottom part of the cowl (?) to get it to fit properly. There is now a slit in the cowl.

I'll crawl under the dash later today and take some pictures.

EDIT: Here are some pictures of the D.S. cowl, the hole from the cable clutch, and the P.S. cowl.

Driver Side Cowl picture by PaintballerCA - Photobucket
Cable Clutch picture by PaintballerCA - Photobucket
Passenger Side Cowl picture by PaintballerCA - Photobucket

GNGREN · Sep 16, 2009

6Stang7 said:
When I look under the dash, am I seeing the bottom part of the cowl; the part where the waters runs down? If so, it looks like the area right around the fresh air towers is what is leaking, so I might be able to repair it without removing the cowl.

I have have the same issue pretty much. I made my own cable clutch conversion when I installed a T-5 and I had to "massage" the bottom part of the cowl (?) to get it to fit properly. There is now a slit in the cowl.

I'll crawl under the dash later today and take some pictures.

Sounds like we have pretty much the same issue though. As you put it when I "massaged" the cowl for clearance I split it. It was more rusted than I had predicted, and I was being careful. It didn't look bad at all from the underside, meaning no pin holes except next to the hat on the drivers side. The plastic hats didn't work for me, as the holes were not covered by them. I am just gonna suck it up and do it right so I never have to worry about it again.

Just got the pictures to load. My cowl didn't look as bad as what yours does underneath. I didn't have the surface rust like that. And I didn't split it where I did the clearancing it was up closer to the hat. Although I did drill into it from the fire wall side, I miss measured/aligned the punch when I hit it from the inside to line the cable hole with the bracket. I caught the bottom by about 1/16th" just enough that the bit went in and wouldn't just ride the slope.

oh9mustang · Sep 16, 2009

Under the fender there is a drain that water drains to the inner fender area from the cowl. If this drain gets plugged or rusted out water will come inside instead of outside. Remove the inner fender and look at the top where the fender and the cowl meat. There should be a drop in the body, like someone took a hammer and hit it once. If the car is relatively rust free, it's most likely leaves that plugged the drain.

6Stang7 · Sep 16, 2009

I pulled the heater box out yesterday and got a complete view of the P.S. cowl. There is more damage here then the D.S., but nothing that I don't think I can fix. Here's some more pictures:

Passenger Side Cowl #2 picture by PaintballerCA - Photobucket
Passenger Side Cowl #5 picture by PaintballerCA - Photobucket

Anyone have any suggestions for how to clean out the cowl through the inner fender guards off? I'm going to try to remove as much rust as I can, seal off the seam around the towers and were the bottom cowl joins the rest of the car, and then fiberglass around the tower. I just want to make sure that I remove anything that could prevent the water from flowing.

6Stang7 · Sep 23, 2009

So maybe I have gone off the deep end here, or maybe I have had a stroke of genius..................or maybe a little of both. Instead of fiberglassing the lower cowl to prevent water from leaking, I am thinking of patching up any holes with some primed sheet metal (to prevent it from rusting), and then seal the bottom of the cowl with the truck bed coatings (Hurculiner). This should make a very good seal, make a strong bond to the metal, and be able to stand up to vibration and heat cycling.

Has anyone else tried this stuff for sealing up parts of there car? If so, how did it work?

hungrymonkey · Sep 23, 2009

Are you removing the cowl vent cover and fixing through the top? Or do you mean going from the bottom and fixing it under the dash?

Personally, if you are going through the top. I would replace the cowls and Por15 over them. I have not had a whole lot of luck with the DIY bed liners. and Por has a very solid reputation.

6Stang7 · Sep 23, 2009

hungrymonkey said:
Are you removing the cowl vent cover and fixing through the top? Or do you mean going from the bottom and fixing it under the dash?

Personally, if you are going through the top. I would replace the cowls and Por15 over them. I have not had a whole lot of luck with the DIY bed liners. and Por has a very solid reputation.

Going from the bottom and fixing it under the dash. This is more or less a band-aid fix for the car while I finish college. That and I need to decided whether to keep the car or sell her off in a few years when I get ready to start working on my GT40 MkI project.

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