I know these kinds of problems can be hard to pin down on any car partly because on the same make and model car, there can be several unrelated causes. My first thought is that there is maybe a drain hole in the cowling that is clogged up, so it fills and dumps to the floor, but I have no evidence of that at all - just a wild guess.

So - I was wondering if there is a particular cause of this problem that is prevalent on this chassis. This happens with the car sitting - not moving or operating - IOW - if it rains hard at night, you get up the next morning and the front passenger side floor is filled (1" deep) with water.

What areas should I focus on as the likely cause?

Thanks for any help.

Check this write up. https://www.gmforum.com/normal-maintainence-138/evap-clean-278997/ There'* a drain in the EVAP, if that plugs up it will fill with water and drain back in to the passenger side floor.

Thanks, Dan.

Wouldn't that only cause problems when the a.c. was being used - not from rain? Or does rain water also get directed to the evap. condensate drain?

Water can drain in to the system and then in to the car. It'* a good place to start. Also, if you have a sunroof, there are drain hoses. If they come unhooked it will drain water in to the car.

No sunroof. The vehicle in your How To is a bit different from my '99 Century, but I will be taking the cowl off (hopefully tomorrow). I think there are a lot of leaves and other debris down there, but whether thats the problem or not I don't know yet. Will report back with what I find.

Can you tell where the water is coming in? If from the floor vents, then it'* likely the EVAP drain.

W bodies of this era have an inherent love to leak water. It'* because where your cabin air filter could be, there'* a rubber strip. If it'* not perfect, it leaks. Another thing is on the front side there'* a plastic vent looking piece, also if not perfect it can leak.

Then you get into a true fix. GM part is #15794785 This is about $5 at a dealer and it'* a permanant fix that channels all water out away from the blower motor area.

My dad had the same problem on his van.as well as a wiper motor frying.When i pulled the cowl to replace to motor i found the cowl full of water and the motor submerged.Why? the drain was clogged with leaves but when it got that full it found its way onto the floor

For some reason I didn't get email noitification on the previous 2 posts - maybe the subscribe feature expires after a couple of days?

Anyway - I figured it out and fixed it. I think Bill Boost37 hit the nail en la cabeza.

There'* a plastic baffle (for lack of a better word, that'* what I'm calling it - BillBoost37 is calling it a plastic vent piece - that'* just as good a name for it, maybe even better) suspended above the cabin air filter - it was way out of position and was funneling water that would have gone down the cowl drain right into the filter - which dumped right to the blower motor.

I put to together some photos of what I found:

Pic 1: As my wife ran a water hose over the passenger side windshield, this is what I saw on the inside with the carpet pulled back off the floor.

Pic 2: Looking up, I see water actively dripping from the top and bottom of the well that the blower motor sits in - see drips hanging on left side of photo, and that icicle-looking think on the right is a steady stream of water. (Maybe this explains why I've had two blower resistor paks go out on me even after replacing the blower motor with a new one?.)

Pic. 3: Here'* looking down into the cowl with the cover removed - drain on left of photo, cabin filter box on right - see blower motor just under where the filter goes.

Pic. 4: Same as previous picture, except with the baffle - what I think BillBoost37 called the plastic vent piece - shown in place. The problem was that that piece had been installed shifted way towards the passenger side, which caught water that would have gone into the drain hole, and dumped it right into the filter, onto the blower. Sorry I don't have a picture of how it was when I took the cover off - at the time, I didn't realize that it was not in the correct position.

Pic. 5: The cowl cover (looking at the underside) has a paper flashing that forms a wall between the drain hole and the filter box to ensure that no water splashes onto the filter. Because that black plastic baffle that was supposed to be over the filter was shifted to the passenger side, the flashing was crunched up against the cover - and some tears were created in the flashing. So with the baffle shifted and the flashing no longer creating the separating wall, water was not only free to flow into but was actually directed into the filter box.

Pic. 6: Closeup of the flashing - see how it was crumpled and torn.

Pic. 7: Went to Lowes and got a 4x4 rubber sheet from the plumbing department, cut it to the approximate size of the original flashing, and pop-riveted it in place over the damaged paper flashing.

Pic. 8: Another view of the flashing repair.

Pic. 9: Here is a new cabin air filter in place (old filter was covered with trash and leaves from the water having been flowing onto it), ready to install the baffle back in the right place.

Pic. 10: Repeat of Pic. 4 - but figured it was worth putting it here to show the correct location of the baffle.

Note: I probably would never have realized that the baffle had been in the wrong position, except, after my suspisions were raised by the crunched/damaged paper flashing, I went back and looked at the old filter, and I could see that some tabs on the baffle had made permanent impressions on the filter - and those impressions were way towards the passenger side from where they would be if the baffle was installed correctly.

We had quite a bit of rain last week, and no rain got in since fixing it. However, with the cold temperatures, and in spite of getting what water out that I could before the repair with a carpet cleaner, paper towels, etc., the thick foam rubber on the underside of the carpet has been taking forever to dry out. So this weekend, I used a small portable heater and fan to warm up and get air circulating in the cabin and especially against the carpet and its padding - everything is bone dry now, will be buttoning everything back up on the interior in just a few minutes.

Anyway - thanks for reading this long post. Thanks for the help.

Thanks for the follow up. I will mark this as fixed to help the next person that comes along.