1986 cowl leak what to do??


New Member
Sep 16, 2021
North carolina
I bought a 1986 GT a couple of months ago, after pulling the carpet to replace it I found some holes in the floor pan and took the car to a metal shop to have them patched.

Turns out those holes were caused by water leaking into the floor from under the dash, I quickly realized that the cowl is probably rusted internally and is leaking water.

From what I’ve read, I think I could take the fender off and have the rusty area repaired that way, but is their another option? Taking off the fender seems to be a daunting task for me because the most work I’ve ever done to a car myself was putting cams in a 2007 mustang, so taking an entire fender off seems difficult, time consuming and dreadful.

I saw on LMR there’s a cowl cover meant for race cars that completely seals off the cowl, but it also removes one of the wiper arms, which I really don’t want to do.

Does anyone know of any slightly easier solutions to this issue other than removing the entire fender and repairing the area? I know the cowl is a common spot for rust on these cars since the area can easily become clogged with debris, but I can’t find much in the way of solutions.
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If you can install a cam, you can take a fender off. It's pretty easy.

However, just be aware that the area of concern might not be under the fender. There's a few areas where water can rust through the cowl. Under the fenders in the corner of the windshield is one, but also inside the actual cowl. If you take your center grill off, you might be able to see inside the cowl. The lower pan slopes towards the pass side to the HVAC inlet and this is a good source of water leaks as well as leaves and grime will accumulate here, remain wet and cause rust issues. The water is supposed to drain into the pass side fender area, but if those same leaves block those channels to the fender area, then the rust can form inside the cowl itself.

Really, you need to scout around and locate the source of the rot. You'll likely need to pull a fender (or two) but you may need to look at the mail cowl itself which won't be a fun repair

This video shows some terrible rust in that area. Yours is likely not this bad but you need to find it

View: https://www.youtube.com/watch?v=4LkpykR9LwI
Your cowl panel drains are probably plugged with leaves or debris
Mustang 5L5 is right pulling the fender may not give you much access
There are 2 cowl drains with rubber plugs that you can squeeze and let debris out
Find them
Also make sure the HVAC evaporator drain is clear
It is the other little rubber plug at the bottom of the HVAC plenum
Good luck