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Rusting Air Vent - How to Replace?!!
Hi All, 

Have just discovered that the air vent intake has rusted. See images. It's under some serious sheet metal. Has anyone replaced this vent? 

It explains why we have rust limited to the floor pans, as this vent obviously sits proud, so that water does not get inside it. Now it funnels the water down into the car!

Can't find a thread on this issue, sorry if I missed it, just point me to it so I don't waste anyone's time.

Thanks, in advance, for your time and thoughts on this.

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Leave death a burnt out castle
Common problem, several threads about it, here's one

“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
Hi, I had the same on both sides on my mach1.
What I ended up doing was to remove the upper cowl area above the air vents by drilling out the welds with a spot weld drill and carefully cutting the upper cowl in a couple of area's so I did not have to remove the entire upper cowl.

[Image: 36276456994_8a42154f97_b.jpg]DSC00364a by karl stroud, on Flickr

[Image: 36299087383_8c813e6b47_b.jpg]DSC00368a by karl stroud, on Flickr

[Image: 36970345581_258c2a13d7_b.jpg]DSC00372a by karl stroud, on Flickr

[Image: 36276457024_37fb38953a_b.jpg]DSC00373a by karl stroud, on Flickr

[Image: 36923300476_80418c4221_b.jpg]DSC00383a by karl stroud, on Flickr

[Image: 36715275040_bcafe0f353_b.jpg]DSC00382a by karl stroud, on Flickr

After I replaced all the rotten metal and rebuilt the vent I reshaped the area slightly to force any water to run away from the vent and toward the main drain, another thing I did was to totally seal around the vent where it attaches to the firewall with a high quality seam sealer to totally stop any future water ingress  ( I also sealed any area in the cowl where water could get between any joins ). The next thing what I thought was worth doing was to make the main drain hole a bit larger so it could not be blocked by leaves.

Cowl rot is really a bummer.  It is common, and difficult to repair correctly.
I went at it from the bottom, to leave the top half of the cowl untouched.  It was a lot of work and after I tacked in the patch panel I hired a welder to finish it up since it was overhead welding.
My two cents.
I would not attempt to patch with sheet metal or with fiberglass or any kind of quick fix. Just go ahead and take the upper cowl off and the lower and replace with new repo panels from Dynacorn. Not easy for sure but will give you new metal in a very structural part of the vehicle. You also want to be sure to put plenty of seam sealer inside before you put the upper cowl back on. Also paint inside the cowl even use weld through primer on the weld flange.
I forget how many hundred welds there are. You should do this with the frame supported and maybe add some braces in the doors to prevent moving.
The cowl is one reason I never was one of these cars with a hose or car wash. I only take water in a bucket and micro fiber towel and wipe the car down and never run water in the cowl, doors or quarter panels. There was ZERO paint inside them except for a little overspray.
When they go back together you should also add the barriers to keep mice and critters out of the heater box and the cowl.
The pics show the 1/4" mesh wire over the heater box and I also put behind the plastic cowl vent grills. I put Stainless Steel pot scrubber pads in the cowl vent drains on each side to stop the entry there. Mice love to build nests in there then pee on the nest and it also holds moisture to make more rust.
The cowl on every year mustang rusts out very early on.
Your tail light panel is the same way. There were parts in the way on the inside of the tail light panel that prevented primer or paint from getting on the metal so they started rusting the first time they were washed. Only took a couple years for even California cars to rust around the tail lights and cowl if washed a lot.
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When a man is in the woods and talks and no women are there is he still wrong??
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