Cowl Rust Cause?

[ursus]

I have always wondered why so many Model A's have rusted out in the lower cowl area on one or both sides of the body, usually both sides. Often, this may be the only part of the car that is rusted out. By rusted out I mean that the sheet metal needs replacement. What makes no sense is that there is no apparent pathway for water to enter or accumulate there.

Can anybody explain this phenomenon? My interest comes from wanting to prevent future rust in the repaired area. Thanks!

[msmaron]

TOTALLY water enters from the seam of the gas tank to the cowl, No phenomenon at all and very very common due to that

[2manycars]

The inside of the cowl at the lower area was probably not painted well, as it is blocked by the floor riser.

[MikeK]

Condensation. Anytime the inside of your windshield is fogged up so is the inside of many sheet metal panels. You just don't see it. You do not need a water leak, just air.

[wrndln]

The problem is that there is a triangle shaped gusset to strengthen the cowl panel on the inside of the cowl. There is a gap between the gusset and the cowl exterior sheetmetal. Salt, water and who knows what else accumulates in the approximate 1/8" space between the gusset and cowl panel and causes rust problems. I have repaired three pair of rusted out cowl on 28 and 29 vehicles. You are definitely correct that this is a problem spot for 28/29 model A's due to years of use on questionable roads. I cut out the exterior panel in the shape of a triangle and butt weld in a patch of the same gauge. The repairs work well - see attached pictures.
Rusty Nelson

[Tom Wesenberg]

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Pretty sure Rusty got his name from all the rust he's repaired.

Just think how few Model A's would be left if they used that nasty, polluting road salt back in the good old days.

[Synchro909]

Originally Posted by wrndln

The problem is that there is a triangle shaped gusset to strengthen the cowl panel on the inside of the cowl. There is a gap between the gusset and the cowl exterior sheetmetal. Salt, water and who knows what else accumulates in the approximate 1/8" space between the gusset and cowl panel and causes rust problems. I have repaired three pair of rusted out cowl on 28 and 29 vehicles. You are definitely correct that this is a problem spot for 28/29 model A's due to years of use on questionable roads. I cut out the exterior panel in the shape of a triangle and butt weld in a patch of the same gauge. The repairs work well - see attached pictures.
Rusty Nelson

Is that patch (2nd picture) overlapping the original metal??? If so, what do you do to stop rust getting into the overlap?

[wrndln]

Synchro909,
No, the patch is butt welded in place. Besides I spray a heavy coat of epoxy primer in the gap between the gusset and the outer sheetmetal.
Rusty Nelson

[SeaSlugs]

The few cabs and cowls ive looked at usualyl have a thick layer of dust/dirt down in that "pocket" - like someone else said mixed with a little condensation it turns to mud and its like keeping a wet sponge on a piece of steel that didnt get painted easily.

Same reasons on modern cars why rear wheel wells, rocker panels, doors, and cab corners rot out - usually not painted, dust and condensation mix and add a pinch of road salt and you got a concoction that will eat anything. It takes years to do and manufactuers will always blame you for them rotting out. Theres a reason Ziebart drills holes and fills these areas with special stuff to prevent contact with the metal.

[Synchro909]

Originally Posted by wrndln

Synchro909,
No, the patch is butt welded in place. Besides I spray a heavy coat of epoxy primer in the gap between the gusset and the outer sheetmetal.
Rusty Nelson

That's good to hear!