Heater Core Area, Vent Cowls, under dash
A couple comments, and guesses...
1) Foam seal:
- The one I have wraps around the bakelite heater fan inlet.
- See pic 2.
- It is now slightly <1/2" x <1/2" in dimension. I would suppose it has shrunk in size over the decades.
- the hardness is similar to the green colored open cell foam you might find in a floral vase; its crispy, not soft (any longer anyway). But, the cells are much finer.
- From the under dash picture 3, you can see how the foam would go into the recess ring UNDER the dash area, and in theory might seal off air leaks. But, it would be hard, regardless of material type to seal off any water from leaking through there, as it would already have the opportunity of a gap (capillary action) and gravity (drip, drip).
- I would think it very hard to water to access this area directly above, as it is covered by the solid cowl between the fresh air vents and the hood latch. And yet... the screws holding the heater fan to the firewall were completely rusted and seized. I ended up wrecking a fan case trying to loosen screws.
My guess is that your latch opening theory has merit...
2) Heater Core box, drain and seals.
- Looking at the last picture, the drain is loosely installed.
- As stated earlier, the top edges of the drain were strong duct (type) taped to the sidewalls of the box.
- The latch pin hole would allow water in.
- The drain should collect that water and send it down through a tube to duck bill inside engine bay.
- More guesses, not great at collecting all water going in there. And any dripping under G's would have it go everywhere...
- the TEAE site has a nice post on this area and sealing the rectangular opening below the heater core.
http://teae.org/heaterdefroster/
- In my case, only the felt on the ends (terminations) of the heater core were present. They wrapped the ends 3/4 of the way around the perimeter. Like a reversed "C", no felt towards cabin.
- These would not prevent water from going in the car and would absorb moisture. I'm of a mind to replace them with a non-absorbing material, but it would have to accept some higher temps.
- The TEAE suggestion is worth a shot. But I also wonder about trapping water in the area. Worst case, it rains so hard the water fills the area and comes into contact with the heater core fins themselves. ?
3) Fresh air vent scuttles
- My guess is that your hoses were removed from the bottom of the vent that you repaired? Or the ends of the hoses were clogged?
- I intend to mastic or sealant the perimeter of the plastic vents to the scuttle when re-riveting, just to prevent any leakage there.
- You will note that we gooped the #$%$# out of the vent scuttle area. Kind of the weak point of the whole car. Can always go back and clean that up. But it looked like hell before the repaint too.