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Post Info TOPIC: Cowl Vent drainage


Poncho Master!

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Cowl Vent drainage


I ran the 2+2 through a car wash and water flowed out below/beside drivers side floor vent. I suspect something is plugged but Im not familiar with how cowl drains.

Looking for ideas on where to clean out. Im guessing that the drain is through the rocker panels. Anyone have drawing or familiar with the vent and drain system?



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Eric - Regina, SK

The Projects:

1935 Chev 3 Window Std Coupe

1957 Chev 2dr 

1967 Mustang Convertible

1969 Firebird 350HO Convertible

1969 Camaro X11-V8

1969 2+2 was a 396

1969 2+2 427

1980 Harley FXWG

1986 CJ7 Jeep

 



Canadian Poncho Superstar!

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The air enters through the cowl screens, goes down by the kick panel vents, then through the rocker panels, and exits just ahead of the rear tires. If you poke your head under the rocker panels, on the inside maybe 3 or 4" ahead of the wheel opening you'll see a hole about 1" square. On my Parisienne, the drivers side hole was covered over with a small piece of sheet metal, and I could hear the water sloshing after going through a car wash, and it'd take quite a while to drain.

When I cut the 70 Parisienne convertible from Jerel apart last spring, I meant to take a photo of the size of the airway through the rocker panel, it's actually quite big.

So yes, I suspect you've got something clogging the flow between the kick panel vents and the exit. Any way to get a plumbers snake down there through the kick panel?



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70 2+2 convertible
70 2+2 hardtop
70 Parisienne hardtop
72 GMC Sierra

 

 



Poncho Master!

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Thanks Cliff. Vincent sent me a text last night and coached me through how to clear it out. 

For reference Ill post the procedure that I used but the credit goes to Vincent.
DCDC5136-916D-48A8-8942-665A49008FE8.jpeg

 

At the rear of the rocker on the inside is a square hole that allows for air and moisture to exit. This hole can become plugged. I used a small hook made of 1/8 steel rod (Old welding rod) to pull garbage out and clear the hole. However when I went to flush the passage there still was water flowing into the car through the foot vent. To clear the portion at the 90, a piece of semi rigid hose was fed through the foot vent until it met an obstruction. Holding the hose firmly into the obstruction I applied compressed air several times and I could hear as it blew the plugged space open. Repeat several times with flushing water from the top of cowl and pulling crap out of the rear drain hole. 

 

Credit goes to Vincent who coached me through the procedure. 



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Eric - Regina, SK

The Projects:

1935 Chev 3 Window Std Coupe

1957 Chev 2dr 

1967 Mustang Convertible

1969 Firebird 350HO Convertible

1969 Camaro X11-V8

1969 2+2 was a 396

1969 2+2 427

1980 Harley FXWG

1986 CJ7 Jeep

 



Canadian Poncho Superstar!

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Good to know. I suspect I'll have to do the same on my 65, as it sat outside under trees for 20 years.



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65 Laurentian post, 67 Grande Parisienne 4 door HT. 
 


Canadian Poncho Superstar!

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I had a Bel Air once that filled the front floor pans with about an inch of water every time it rained. Water came in around the vents just like yours. It turned out that  - wherever the car came from - the rockers were filled with silt or sand that prevented the water from running out the back as it does in my 68 Caprice. I removed the rear flap as Clint described and flushed the rockers for hours with high pressure water. Once I got the silt and sand out I never had the problem again. 



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62 Catalina 2 dr post project

69 Parisienne 2 dr ht 427

68 Impala SS427 convt project

Misc. 66-69 BB Chevy B bodies

55 Bel Air 2 dr post 265PP/PG

11 C63 AMG Mercedes sedan

 



Canadian Poncho Superstar!

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Any progress Eric?

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70 2+2 convertible
70 2+2 hardtop
70 Parisienne hardtop
72 GMC Sierra

 

 



A Poncho Legend!

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seventy2plus2 wrote:

Any progress Eric?


 

dcneric wrote:

At the rear of the rocker on the inside is a square hole that allows for air and moisture to exit. This hole can become plugged. I used a small hook made of 1/8 steel rod (Old welding rod) to pull garbage out and clear the hole. However when I went to flush the passage there still was water flowing into the car through the foot vent. To clear the portion at the 90, a piece of semi rigid hose was fed through the foot vent until it met an obstruction. Holding the hose firmly into the obstruction I applied compressed air several times and I could hear as it blew the plugged space open. Repeat several times with flushing water from the top of cowl and pulling crap out of the rear drain hole. 

 Credit goes to Vincent who coached me through the procedure. 


 



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Prince Edward Island

'64 Parisienne CS "barn find" - last on the road in '86 ... Owner Protection Plan booklet, original paint, original near-mint aqua interior, original aqua GM floor mats, original 283, factory posi, and original rust.



Guru

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As mentioned the most obvious areas of trouble are the drain opening on the back inside of each rocker and also the rather small hole at the bottom of the cowl plenum into the front of the rocker. The usual culprits in the front plenum are rotted vegetation (leaves etc) that form a water tight sludge that blocks the drain, at the back of the rocker it is often sand, grit and rust scale that blocks the hole. I'd start at the hole on the back of the rocker, your finger will fit and usually you can work the gunk loose. If that is clear already and/or water wont flow to there you have to remove the kick panels, then you can reach down into the plenum and scoop the gunk out. When reinstalling the kick panel make sure you reseal the vent against the body at the vent opening as driving in the rain can allow water to seep into the footwell even once the drains are opened up.

The very course chicken wire on top of the cowl was the design flaw in what was other a good design to keep the plenum and rockers clean and dry. in later years they went with a very fine mesh instead of the chicken wire, this massively reduced the problem. I as a habit flush out the cowl right away every time I buy an old car. Even if you don't have flooding problems the presence of gunk in those areas will really accelerate corrosion in areas very difficult and costly to repair. I also wash out the windshield and back glass surrounds to remove the gunk while inspecting for any leaks. You don't want water accumulating under your trunk mat.

BTW, running a 51 year old car through a carwash probably isn't the best idea. The brush washes are brutal on paint and catching trim moldings and the touchless washes operate at water pressures that our cars were never designed to withstand even when new. With 50 year old weatherstripping or junk repro weatherstripping these cars are even more prone to leakage.

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John

Montreal 

16 1969 American Pontiacs

and a 1969 Canadian 2+2 Hardtop

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