Annoying leak dead-center of the firewall
 

So my '88 LeSabre has been leaking. Badly. No surprise, right? So I replaced the door seals and had my windshield resealed and I thought I was golden.

Nope. I'm getting a trickle of water coming in from the dead center of the firewall and tricklin in on the exhaust hump. I found Don's awesome anti-leak post and read it.

From his experiences, I found that the HVAC fresh air intake has a seal around it that leaks. So, I RTV'd the crap out of it. I also read that the PS wiper arm can leak into the HVAC opening as well so I RTV'd that too. I put my cowl and metal trim strip back on but no dice. Still leaks.

I've noticed recently that there is some irregulatiry with a part though. You know that thin, long black piece of metal that is screwed down at the base of the windshield? I've noticed that some cars have a rubber seal between it and the glass while other cars do not. My '88 doesn't not have this seal...

Also, my plastic cowl doesn't seem to fit very snugly against the metal frame. Should I get some strip caulk and seal the perimeter of the plastic cowl?

Could water be getting in from these sources where they are supposed to be sealed?

If not, where else should I look?

Edit:

I *think* I might have gotten it already. My theory about the lack of seals around the cowl might be correct. I had some extra foam insulation tape laying around so I ran it the length of the metal trim piece. I also ran some just below where the glass sits on the frame. I hosed it down real good and so far no leaks. I sprayed along the firewall and I got a leak, but it was in a spot I've never gotten them before on the passenger side of the firewall. I followed it up on the engine bay side to where a large pipe and some wires go into the blower box. Its sealed with what looks like tar paper so I think some RTV will do it good. Shouldn't matter anyway because theres *supposed* to be a plastic cover over the wiring and relays but I had it off for the purpose of finding my leaks.

I'm going to wait for the next good rain storm and if I don't get any more leaks then I'm going to call it good and start putting my carpet back in :D

Edit 2:

Well, I think I spoke too soon. I went back out and found one small trickle that made it through. So I'm thinking that If I get some rope caulk and go around the perimeter of the cowl that I should be OK. I think too much water is getting in under it and its dripping down into my hvac system or something.

Could it be the heater core? Does it smell like coolant?

Not the HC. It usually leaks the most while the engine is off and the car is parked. And I can make it "leak" with a garden hose.

leak
 

You need to pull the carpet back and water test it to follow the leak path. Otherwise its like grasping at straws.

Interior is gutted. I can't tell exactly where the water is coming from as there is a big black plastic panel that I don't see how to remove at the base of the lower dash against the interior firewall.

Any thoughts on how to get this out?