Leaking inside the firewall (into the cab) when it rains?

[TimberwolfFXDL]

What could be causing this?  I have an 84 C10.  The interior is stripped out completely right now.  I keep getting puddles on the floor when it rains though.  I noticed the factor insulation on the firewall is damp under the heater box plenum.

Is rain able to make it in there through the gutter area between the wipers?

Any other ideas?

[Jason S]

Just a few thoughts: Rust holes in the cowl area, leaking windshield gasket, plenums at the kick panel not sealed, missing hood seal and underhood heater box not sealed to cab. 

[TimberwolfFXDL]

I don't think the cowl is rusted, and there's no water anywhere near the kick panels.  Heater box is well sealed to the firewall. Windshield seal is tight too.  The weather strip between the hood and cowl vent is missing though.  Seems like that would just allow water into the engine compartment though.

Guess I'll have to do some more detective work

[Jason S]

Others should chime in on the matter.  Without the hood seal, if water were to trickle down the firewall it might find it's way inside through the firewall at the heater core connection. 

You might have someone spray water over the front and then look from the inside of the cab to see where your leak is coming from.

[Blazin]

Does it have cab lights? if so they can leak inside the roof and run down to the floor. It doesn't take much of a rust hole for water to get in from the cowl.

[VileZambonie]

Get a new cowl seal and install it. Reference this as well

http://forum.73-87chevytrucks.com/smforum/index.php/topic,22630.0.html

[TimberwolfFXDL]

Thanks, I will check that out.  Might be easier to track the water flow now... I stripped the floor pans yesterday and it's raining today.  Might give me a tell tale surface rust pattern to follow.