Water coming in on passenger side under heater core, but only when it rains
 

1997 Z71... When it rains, water comes in pretty heavy on the passenger side floorboard, through the bottom of the heater core. (not a heater core leak though). I think it only does this when driving also, not sitting still. It'll have pinestraw, dirt, misc. stuff coming in also. Is there a drain hose or something that could possibly be stopped up?

RE: Water coming in on passenger side under heater core, but only when it rains
 

well, the same thing happened on my current Grand Prix. Completely different vehicles, but probably the same answer. The water runs down the windshield and under the plastic lip at the bottom (instead of over it and through the channels to run the water off). The water then goes down, on the engine side of the firewall until it gets to the heater core, where it pools and runs inside.

If it is a drain, they usually run down on the inside of the fenders at the base of the windshield. I can't remember my '94 anymore to be exactly sure (sold it a few months ago).

RE: Water coming in on passenger side under heater core, but only when it rains
 

sure its not a/c water?... sounds like the drain is plugged..OR the rubber elbow fell off that points down to the road

RE: Water coming in on passenger side under heater core, but only when it rains
 

use silicon around the heater core. mine did the same thing.

RE: Water coming in on passenger side under heater core, but only when it rains
 

Appreciate the reply, but no, I'm positive it's not the a/c water because it clearly drains onto the ground. This water only comes in when its raining, and the vehicle is moving.

RE: Water coming in on passenger side under heater core, but only when it rains
 

must be a plug missing somewhere if itsonly when moving...look at the antenna cable grommett good as well...near the a/c drier

RE: Water coming in on passenger side under heater core, but only when it rains
 

Argon,
I did see that the "thing" (for lack of a name for it) at the bottom of the windshield, between the hood and windshield where the wipers are connected is broke on that side. Could this be the problem? I haven't checked the grommett out yet as you were suggesting.

RE: Water coming in on passenger side under heater core, but only when it rains
 

you mean the plastic grille?..no,water travels through the grill and is guided out....

RE: Water coming in on passenger side under heater core, but only when it rains
 

Where does the outside air enter the cabin? Is there a lot of the same material under the grill as what's coming into the cab? Do you even have pine trees where you live? I though the fresh air entered through the grill.

RE: Water coming in on passenger side under heater core, but only when it rains
 

Check the seal on the windshield. I had the same problem on my wife's minivan. Completely puddled up the floorboard. Rain was being blown through a break in the seal. Pull the flooring or carpet out for awhile. You'll never find the leak if you leave the carpet in. It's easier to tell where it's coming from on naked metal.