I am replacing my heater box/ plentium chamber and my cowl vent was leaking so i replaced the seal from the heater box to the cowl vent. I dont want to put the heater box and plentium chamber back on until i am sure i have stopped the leak. so my question is where does the cowl vent drain to, i noticed that it runs straight to the heater box so is the water supposed to drain in to my heater box or what.
Thanks,
1966stang

 

there are small openings on both sides of the cowl that are covered by the fenders. on my 66 the drains got blocked over time and rusted out the vent risers. to stop the leaking i had to replace the inner and outer cowl panel..... not a small job!!!!! i ended up taking the complete dash apart plus remove the hood, windsheild and fenders.
if your car is not rusted just blow compressed air from the cowl vents toward the fenders of the car, you'll see the dust and dirt fly from inside the fender to the door jam and inner fender panel.

good luck !!!!

 

You can also see if the cowl is leaking by laying up under the dash with a flashlight and have someone else run hose with running water poring (maybe just trickling) through the vent at the base of the windshield. If your cowl is leaking, you will see water coming from around were the heater attached to the lower cowl. Since your heater is out, this is the ideal time to do this.
Do not let a leaky cowl go unchecked for too long. Your floor boards will go next, and then your frame rails and then … I am speaking from personal experience. Please, nobody report me for Mustang neglect.

 

Unchecked, the cowls might turn out like these[:'(]




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That must have been fun to repair, hope mines not like that.

 

Cusbuild,
You seem to be preceding me in all of the jobs I am about to undertake. I am about to do the same fix to my 68. How did you seal the inside seam on the cowl box after you welded it together? I am worried that this seam will rust because it is exposed to the elements and is not accusable for sealing after the cowl box has been welded back together.

 

Haven't replaced the cowl yet want to get it painted inside prior to welding it back together. You have me thinking though, because I hadn't thought about that. My first thought is that once it primered with weldable primer and of course the interior of the cowl is fully primered and painted, I would "think" that the flanges once welded would be safe from rusting once all of the sealer is applied to the outside. My reasoning behind this would be that the seam didn't rust the cowl/ highhats rusted away. I had to still drill out ALL of the spot welds and seperate the two halves, but the damage was from the crap inside the cowl and from the orginal Ford engineering/assembly process that welded it together prior to primer. If in 65' Ford would have had a dip process for applying primer Mustang owners would be a much happier group in general. Beyond that I don't really know any type of sealer that could be applied between the two flanges I would think would be destroyed in the welding process or would catch fire which isn't good either. Don't really know and now I will be thinking about it for a while. I know a couple of resto shops here in Indy I may have to give one of them a call and see if they will tell me what they do.