Outside air leak flowing in from under dash

[SuicideDoorLincoln]

Has anyone on here every experienced cold air coming in from under the dash while driving in the winter on a 74-78 c body? Seems to be coming from the drivers side maybe up around or above the fuse box? I've looked under the dash and on the firewall under hood and do not see any body plugs missing or removed. Just seeing if this was a common problem or a isolated incident. The auto temp 2 works as it should if that matters? It has to be a decent leak as if you held your hand under the dash with a handful of feathers it would knock them off onto the floor.

 

[saylor]

do you have fresh air vents in there? thats about the spot where they would be / where you would feel it. on my 68 plymouth, there are vents with a cable control to open/close them.

- saylor

 

[SuicideDoorLincoln]

No it don't have those. Wish it did . Be a easy fix.

 

[75LandYacht]

Hey Suicide.. Yes, My 75 NYB has that same issue, But what I found was that the driver side Cowl has some rust just above the steering column area. I found it when I was replacing my Wiper Arm Linkage bushing. You can't see the hole from under the dash due al the wires and stuff, but if you pull the plastic trash screens from your Cowl and use a good flashlight you'll be able to see it, as long as your cowl area is clean / clear of the leaves and stuff that accumulate there over the years. Just my 2 cents.

 

[SuicideDoorLincoln]

I bet I got the same the problem . I have a small 1" hole on driver and passenger side that's rotted vertically but it just leads to the cowl. I'll have to investigate . Explains why when I put a trouble light under the dash on both sides I could never see light under the hood in the dark

 

[75LandYacht]

I have the same issue on the Pass side as well, Just not as bad. So while you have the screens off, check the entire cowl out, and clean it too. Maybe even able to patch them while your in there. I have to wait till spring to do mine. Here's a pic of the Pass side. Although the rust hole isn't that defining in the pic, you'll know what to look for when you open yours up. That High Hat you see is where the air comes in when your Vents are open. Pretty common rust area on both sides since this area was not really protected / treated when the car was painted new.

 

[cantflip]

Man... that's a PITA to get in to fix... How are you planning to do that?

 

[1978 NYB]

Use a shop vac and feed the hose down in to the cowl. It will go down pretty deep in the cowl.

 

[SuicideDoorLincoln]

Silicone , jb weld. I personally would paint it with Por 15 first to kill the rust then push gas tank epoxy or 3 part epoxy in the hole.

 

[Mr C]

Did the road noise appreciably increase with this? I've always found that if air is coming in from outside the car, it gets noisy too. If it's relatively quiet, perhaps a hose came off inside the car? Like the ones leading to the drivers side dash vents?

 

[SuicideDoorLincoln]

I didn't have any road noise .... I thought the same thing too though... I'll update you guys this week on what it is. Not to get off topic but , I seen your 2 black imperials for sale about a week to late....I woulda have gladly bought them for advertised price sight unseen. 4 door is my favorite and will never find another like it

 

[SuicideDoorLincoln]

Update. My cold draft was the same problem as yours 78 nyb. I had a fist size hold up high out of the water drain trough . Por 15'd it then sealed it with expanding foam.... Seemed to work... Doused it good with a water hose no leaks. A guy would have to completely pull the dash & wiring or cut the cowl to fix it right. I've parted & completely dismantled 3 1974 imperials storing parts in my garage & none of them had this firewall rot

 

[cantflip]

Update. My cold draft was the same problem as yours 78 nyb. I had a fist size hold up high out of the water drain trough . Por 15'd it then sealed it with expanding foam.... Seemed to work... Doused it good with a water hose no leaks. A guy would have to completely pull the dash & wiring or cut the cowl to fix it right. I've parted & completely dismantled 3 1974 imperials storing parts in my garage & none of them had this firewall rot

I am certain the location caused the factory to not seal the metal as well as other areas. Just like it made it so difficult to get into for repairs. Your fix isn't exactly what I imagined, but is close enough... that is not a place to simply weld in a patch without serious disassembly of the interior. the only upside is nobody will ever see it.

 

[SuicideDoorLincoln]

Yea I didn't care for fixing it that way either but the hole won't get any worse with por 15 on it. My car see's very little rain and no winters so it'll do until it ever gets a full resto

 

[75LandYacht]

I bought a POR-15 kit to address the rust, I was then going too.. Don't judge me on this one!! lol, But I was then going to put some foil tape over the POR-15 and spray that rubberized undercoating all over it.. I said don't judge me!! ;)

Man... that's a PITA to get in to fix... How are you planning to do that?

 

[cantflip]

No judging... That's actually close to what I imagined my patch would be... the spray foam solution was good to... but I wouldn't want it to get wet, the can "open cell" stuff could become a sponge.

Dynamat type product was my first thought, but I bet a good asphalt tape would have worked. What a crazy place to have to deal with when everything else looks good. It is possible I would have lost my mind and stripped the car... but I'm not seeing that as a wise move, more the utterly insane anal repair, just cause its correct doesn't make it right sometimes.

 

[SuicideDoorLincoln]

Yea I contemplated asphalt tape but I was worried about it contracting in bitter cold and lifting ..... This expanding foam is water proof type. Water beads off it

 

[cantflip]

Yea I contemplated asphalt tape but I was worried about it contracting in bitter cold and lifting ..... This expanding foam is water proof type. Water beads off it

No criticism meant... off hand thought. I have just been "armchair engineering" this issue... I hope to never have to deal with it, but you never know.

 

[SuicideDoorLincoln]

None taken