I need serious help here! I just got my 65 coupe back up and running. I took it out for a spin and it started raining. I then realized that I forgot to put my cowl cover back on. It seemed like water came in from everywhere! My wife said that she saw it coming in from around the windshield and from somewhere under the dash (I am assuming the cowl vents).
    I don't know what to do here. I just had the front and rear windshields resealed by a local shop, but I am not sure if they warranty it against leaks due to the car being so old. I will contact that shop on Monday and see about taking it back in.
    One quick question about what sealant to use for the windshields. Should you use the type that dries hard, or should you use the type that stays tacky? A Safelite guy told me that you should use the tacky stuff, but the shop I took it to said that you should use the hard stuff. Which is right?
    The other question I have is about the cowl. I have a Vintage Air Sure Fit A/C unit on the car now and I have no use for the cowl vents. Can you cut out the vent between the hood and the windshield and weld in solid sheet metal instead, or will this have adverse affects on the car?
    If anyone knows of a GOOD classic mustang repair shop around central Florida could you please tell me. Everyone that works on my car seems like they have no idea what they are doing. Whatever I take the car in for still has the same problem even after they say they fixed it! I am getting really frustrated with this car! Thanks for any help or info!  

Its hard to distinguish between a leak in the lower left or right of the windshield and a leak in the cowl vents. But run a hose into the cowl when its dry out and see if its leaking inside. That should tell you where the leak is. A whole heck of a lot of mustangs have bad cowls and its a nasty problem to fix and expensive if you have it done. The new sheetmetal for the upper and lower cowl is now available. You can also try the "hats" which are a plastic tube stuck up the vent stack with a sealant surrounding them, it does work sometimes. I am not familiar with the Classic Air but where does it get fresh air if not from the cowl vents ???  My bet is that it takes it from the passenger side cowl vent just like the original heater and you just werent aware of it. You need fresh air in the car, A/C or not. Any mustang restorer has done the cowl hats and most have done the full cowl complete repair. There is a big difference in price though. I suspect the hats are somewhere around $300-500(guess?) and the full repair is probably ten times that. The cowl is always the first thing I check on a prospective Mustang purchase as I have done the full repair and its a booger believe me. Good luck  

I just put one of the plastic "hats" in the passenger side in a 66 that had this problem.  It wasn't difficult.  I took the heater/vent assemply out and the opening is above it.  Fortunately mine was not rusted to the point that the plastic hat would not work.  I cleaned the rust up with a wire brush wheel in an electric drill, sprayed it with a rust inhibiting paint, thoroughly coated the hat with silicone sealant and slipped it in.  If it lasts a few years, great.  I don't know what the driver's side repair will be like.  This one isn't leaking there.  

I put the plastic hat in the drivers side last night.  The vent was clogged with mice nest(s) and leaves and was quite nasty.  Again, I was lucky.  It hadn't rusted through so I cleaned it up and put the hat in.  Two sheet metal nuts hold the vent assembly in.  It was tricky to get it out of the way and make room to put the hat in but overall, it was an easy job.  I am working on a $500 66 that I probably shouldn't have bought.  I am not restoring it.  I am repairing everything I can and making it a driver.  It had been run into the ground by a couple of teenagers and then parked in a back yard and/or basement for many years.  Pour water in your cown vent and see where it shows up.  

3M makes a sort of tacky glue sealant that is recommended my most classic Mustang owners for sealing the windshield.  But, if you had the windshield professionally put in, and the water is actually leaking from the seal on the windshield, then it would be a warranty issue.  I would think any reputable company would fix the problem that they created.  About the cowls.....Either do it right by replacing the entire cowl, or keep using your covers and not expect any fresh air.  

There is a Tech article that covers windshield replacement here http://www.mustangmonthly.com/techarticles/mump_0708_ford_mustang_windshield_glass_replacement/index.html.
Warranties from places that don't know the proper materials to use are useless and a waste of time and money. Butyl type sealants stay soft and flexible and work but are messy. Sealants that get hard will fail because these old unibody cars are flexible.

cush  

It's probably not your windshield.... if your cowl vent cover is off it's almost definitely coming in from the vents.... they're prone to leak by design, and difficult to fix.  You've got to pop the cowl top off (136 spotwelds) and repair it from the top to do it right.  Sorry if it's not what you wanted to hear..... I've been down that road before.... it aint pretty.  Put your cover back on and drive your car.


Good luck!

KT.