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Clearing cowl drains to stop water leaks on vintage cars

pivots

The cowl is that grille by the windshield, a common fixture on cars since fresh air heating and ventilation became common. Automakers put in drains to deal with any water that gets in, but, until the 1990s, did little to keep leaves and twigs out. Most older cars, and even some newer cars, will clog their cowl drains from time to time, if driven or left outside in the fall.

cowl drain

On many cars, one of the drains was behind the windshield wiper motor. In many, including A-bodies, there are small holes between the fender and the firewall, one on each side of the car. There is usually another drain for the vent fan.

fan drain

Many cars had cowl drain flaps to cover the drains and prevent detritus from entering; these can get stuck in place or seal themselves shut, but the aftemarket sells them for under $10. Owners of 1975-76 Valiants (and possibly other cars) can likely get a 1974 unit (some aftermarket suppliers appear to believe that Chrysler ended production in 1974, but many of the 1975 and 1976 models kept the same parts.)

Valiants and related cars (Darts, Dusters, etc) often leaked through the windshield wiper pivots. While the water that gets in should go into the cowl, in practice, on the 1968-and-newer cars, it tends to go straight down into the dashboard (and you can see the pivot holes if you lower the wiper assembly so this is by design). Replacing the pivot seals should fix it; use a sealant in addition to new seals.

Gene Yetter wrote:

Cleaning in the Volaré engine compartment yesterday, I gave a little nudge to an unknown piece of rubber fitted against the firewall [the cowl drain] and out came a flow of water. ... After sopping up the water and poking my finger around in the space I dislodged a bunch of leaves and sludge. Then I began to make sense of this incident. There are two other similar pieces of rubber on the firewall, three altogether; two towards the sides and one in the middle. A couple of weeks ago I saw some serious corrosion under the opening in the middle of the firewall. I scraped it with an abrasive pad and applied some anti-rust primer. I did the best I could cleaning up rust I could see. Yesterday, I covered the anti-rust primer with satin black Rustoleum. But there's probably more rust in the area of the middle drain that I can’t see.

Phil Gatto added, “When it rained, gallons of water would literally pour on to the front passenger floorboards [of my 1971 Dodge Charger]. I traced it to that rubber flap. I took the flap off and it was totally clogged with dirt from crushed leaves. There was no rust but this was 20 years ago. After cleaning it out all was well. I had the same problem with my 2011 Dodge Avenger, but there was no flap that I could find and so I took it to the dealer. They said that car has two drains and both were clogged. They are much harder to get to on the Avenger, though easy for someone with a lift. They cleaned them out and I haven't had any trouble since.”

On the 1970s Valiant/Dart, there is an additional drain for the air conditioner condensate which also clogs, which starts at back of the “big black box” on the passenger side (covering the evaporator), makes a 90° turn out in the open, and goes through the firewall. Over time this too can clog.

hose

a/c drain

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