[658Chevy]

I've been fighting a leak onto the passenger floor boards on my '69 for a while. I found that it's leaking from the uppermost, forward-most, right hand corner under the dash. It's coming from a recess in a bunch of angled flanges of metal that makes it almost impossible to get in there and seal from under the dash.

The car only leaks parked at a angle tilting to the passenger side (90% of curb-side situations). There are two small factory holes on top of the cowl, in the corner where the windshield and the fender meet. The leak will start up again if I pour water in those two holes. I know the leak is primarily from inside (under those holes), but I've been thinking of sealing those two factory holes as a band aid.

I know those holes are from the factory, and that they are there to drain water accumulating on the cowl. As far as I can tell, if I plug those holes, the most that will happen is that water may eventually spill over the firewall inside the engine compartment.

Anyone have any insight on this? Will there be a big problem in sealing those cowl holes?

 

[cheveslakr]

Not sure I follow this but IIRC the cowl does have plugs, 1 per side, already. The water from the cowl area is designed to drain to each side and down the firewall skirt and out. What may be the issue is a heater core leak??

Jerry

 

[658Chevy]

Jerry, thanks for the response.

It's not a heater core issue as it only leaks when it's raining hard, and when the car is tilted toward the passenger side. It doesn't do it when the heater is on, which during the winter is almost always. Also, with the glove box and passenger vent removed, I can see the source of the leak. It's way, way up in the top most corner under the dash. It's not the windshield as I've had that checked. When I pour water directly onto the windshield, there is no leak. When I pour water directly into those two factory holes, the leak comes back.

I may not be using the word "cowl" correctly. To see the holes you first have to pop the hood. Then you go to the base of the windshield and follow it to the passenger fender, and about four inches forward from the windshield are two small factory holes, about 1/4" diameter. Both driver and passenger sides of the car have them.

I'm aware that these holes are not the cause of the leak -- the cause is some gaps in the 43-year metal under the dash. However, when I plug those two holes, the leak stops.

Without taking everything apart, I'm not able to see the architecture inside that exists underneath the windshield and behind the firewall. The car presently drains fine behind both front wheels and in front of both back wheels.

From what I've observed, I think it's isolated to a channel fed only by those two holes I mentioned. It's clear the factory put them there for drainage. What I'm wondering is if there would be any significant problem to plugging those holes.

Again, this is only a band aid. When I take the car apart in the future, I plan on properly sealing all the seams. Until then, I want to keep water out of the cab.