It can be a time consuming process to isolate the cause of water leaks. In most cases the carpet must be at least pulled back and some interior trim pieces removed as necessary in order to see where the water is coming in. Water testing will involve someone inside the car with a flashlight while a helper carefully sprays the outside. Wen water is seen entering the interior, care must be taken spraying the water to try and isolate the entry point. Door seals, windshield seals, and cowl seals are some common places to find leaks. If when water testing your 2000 Oldsmobile Intrigue you fined water coming out of the heater box chances are the water is coming in the air inlet under the right side cowl.
I had the same exact problem with my 2000 Intrigue. Upon the advice of a friend in the auto glass industry, he told me it's very common for the seal around the cabin air inlet to slip out of place. This seals the inlet against the bottom of the RH (passenger side) cowling cover as the previous answer states. Remove the RH wiper arm and cowling cover. The inlet is right there and it should be obvious if the seal is out of place. You might even see "trails" in the dust made by leaking water. I put 3 or 4 small dabs of silicone sealant on the bottom of the seal and reinstalled the seal in the proper position. Use just small dabs of sealant to hold the seal in place. This took care of my problem and I hope it works for you.
Hay im having this same problem but the water is on the drivers side an im a new car owner an have no idea what im looking for...just know their is water moving around for a few days an then boom its all on the floor an it builds up an keeps dumping ? what to do HELP!
pic would be nice if any 1 cound help with my 2000 intrigue GL