Cowl drain

I am trying to track down a major leak in my 69 roadrunner. The floor gets wet every time I wash the car. I currently have the heater box out, replaced the heater core (it was bypassed and certainly not the problem), replaced wiper pivot gaskets and now I'm trying to figure out how to check out the cowl drains and overall condition of the cowl. I am not sure where the cowl drains are and where it is prone to leaking. Windshield gasket is next but it has been replaced already (couple yrs ago). I'm trying to cover all bases here and could use some assistance! How do I clean the cowl drains and what else could be leaking? I don't see any rust holes in the cowl under the dash.... Car is a restored driver so I am limited in what I can pull apart. Please help!!!!

The new windshield gaskets dont seem to fit the glass as tight as the original ones.(where the glass sits in the gasket channel) I had to use sealer inside the gasket where the glass sits to keep it from leaking. dont forget to check the wiper motor seal at the cowl. cowl drains are on each side on top but are behind the front fenders. you can get to them by taking the rear splash shields off.

jburt said:

The new windshield gaskets dont seem to fit the glass as tight as the original ones.(where the glass sits in the gasket channel) I had to use sealer inside the gasket where the glass sits to keep it from leaking. dont forget to check the wiper motor seal at the cowl. cowl drains are on each side on top but are behind the front fenders. you can get to them by taking the rear splash shields off.

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Agree.

And to add to this, there is seam sealer on the side of the cowl under the cowl drains, and it was usually done poorly when the cars were built. On my car, the seam sealer on one side was put in so that it actually captured water and directed it between the seam sealer and the body. You can see it in the attached picture of my passenger side area under the cowl drains. I would take off the rear splash shields and check this area with a flashlight and mirror to ensure it is in good shape...

Thanks for posting.

I have a similar leak causing my floors to get wet. I'll be watching this thread.

Thank you for your replies. Is there a non intrusive way to repair poorly done seam sealer if that is part of the issue?

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Easiest way to remove the splash shields on a car that was painted while assembled? A pic of the area in question would help also! Hsorman... The pic helps but can't see what your referring to? Not sure what I'm looking at!

Turn the heater blower on high , soap up the windshield (dish soap and water). Look for bubbles to start expanding. Car may have so many leaks this method won't work. Next step soap up the windshield and blow compressed air around the edge from the inside. Try laying on the floor upside down with your head under the dash. Use a led flashlight and have someone start running water on the car. Have them start low and work their way up. It may take awhile for the water to find it's way through a crack to take your time and work slow. Also just because you see where it comes in the car doesn't mean that's where the entrance point actually starts. Hated water leaks when I was at a the dealership, time consuming.
Doug

Dane,

This is the area just in front of the doors - The backs of the fenders cover this area up.

Here is another shot of the driver's side. You can see the bottom door hinge here...


Here is a picture of my car after the bodywork. The area I am talking about is just in front of the doors. If you look closely, you will see the cowl drain in this picture. Look straight forward from the upper hinge until you get to a black oval hole. This is the cowl drain...

Perfect!!! That helps. Thanks a million

Working under the dash--take out the front seat. That will save you a lot of pain and aggravation.................................MO

Where is the water leaking at? Is it sporadically across the floor or does it leak in specific locations? Good way to troubleshoot the leaks is to just lay a hose on the roof, let the water run down the windshield and observe from inside the car. Windshield seals and wiper pivot seals are usually the culprit, but unfortunately there is a darker, deadlier cancer that our B-Bodies can have an issue with as well.........The inner cowl fresh air plenum's. Their located at the top of your fresh air vent boxes. Typically what happens is dust, dirt, leaves, mice nest's, pine needles drop in the cowl through the cowl vent slots. From there that garbage settle's around the lowest point inside your cowl, and you guessed it, right at the fresh air plenum's. After the years go by rust set's in and it rot's away the plenums and surrounding metal. When that happens, water goes down inside the cowl vent openings and run's right down inside the car's fresh air vent boxes and on to your floorboards. Bad new's! The real bad new's is that to properly fix them, the outer cowl needs to be removed to gain access, and obviously that's no walk in the park. I've seen other guys just seal them off from the inside of the car, but then they have no fresh air vent and no outside air making it to the heater box/ac as well.

If you need to inspect your plenum's, you can remove the driver side fresh air box pretty easily. Inspect the rubber boot/seal at the top of it. With a mirror/flashlight you can inspect the condition of you plenum.



The above pic is not a big bowl of nasty-*** popcorn sitting around since 1984. It's a mouse nest filled plenum. Amazingly this plenum on my 69 roadrunner was not rotted through, but the pic should show you what a poor design this is for longevity (being all the garbage & moisture is funneled right to it.) Unfortunately my '68 coronet did not fare as well and I routed for a bit more work, but a bit more drier feet.

Good luck which ever route you need to go to fix it. Wet floors are obviously a horrible thing to begin with.

Wow! Great reply! I actually removed the air box and splash shields to access the drains. The plenum appears to be in great shape but there was sand (from sandblasting I assume) packed to the rim. I cleaned out all of the sand through the drain and by hand from under the dash. What a job! I'm in ohio so it is too cold to start playing with water. I will try the hose deal though. My first though is that the sand was not helping matters and may have been causing it to overflow

Those one piece rubber gaskets from the back of the wiper motor to the firewall can be leakers as well. Just something to check if you have that type of gasket on the back of the wiper motor. I replace those with the dense foam gasket and that usually clears up a wiper motor gasket leak.

jburt said:

The new windshield gaskets dont seem to fit the glass as tight as the original ones.(where the glass sits in the gasket channel) I had to use sealer inside the gasket where the glass sits to keep it from leaking.

Click to expand...

This would be my first place to investigate also. Have someone take a pump sprayer with water and squirt in each lower corner of the glass while you lay on your back inside on the floor. It wont take much to see where the problem is. It is alot easier if you remove your front seats first.

Mine was leaking at the cowl seam itself, from the sealer falling off due to age. And crap in cowl. Vacuumed out with shop-vac and resealed cowl seam under dash and down sides. Leaked fixed. Also used a wire to clean cowl drains from inside out.

Wow! Great reply! I actually removed the air box and splash shields to access the drains. The plenum appears to be in great shape but there was sand (from sandblasting I assume) packed to the rim. I cleaned out all of the sand through the drain and by hand from under the dash. What a job! I'm in ohio so it is too cold to start playing with water. I will try the hose deal though. My first though is that the sand was not helping matters and may have been causing it to overflow

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Well that's great to hear! Lotta great ideas these guys are all giving to help you find your issue. Hope it works out well for you DaneBisel.

Thank you to everyone that replied. I am in the process of restoring my heater box so I have it out. I bought all new firewall gaskets and plan to spray the windshield as soon as weather permits. I have to take the windshield out this spring (to remove and rewire the dash) so I will address the window (if it leaks) at that time. Problem is finding someone that knows how to install those tricky buggers. Definitely having tye removal and installation done by a professional....with insurance!!!!

This guy would be an excellent resource to get some real good info on a windshield install: