I have a 2001 Buick LeSabre Limited with 90,000 miles that gets a bit of wet floor pad under the gas pedal after driving for several hours. It'* actually only noticeable the next day. I'd guess that it'* coming from a tiny leak of some kind in the heater core stuff. Since it seems small and quite pricey for servicing this area, I thought I'd try an additive that is supposed to stop small leaks - say Bar'* stop-leak product. Do you think this a reasonable and suitable short-term solution? Any problems associated with this? Thanks.

Are you sure it'* coolant leaking in?

Hmmm...good question, but it'* difficult to tell. I plan to check after no rain (today) and after more rain (tomorrow). The car is kept outside. I've found no wetness above the gas pedal area, but the warmness of the heater area may evaporate it.

Turn the car on, switch it over to high heat, and turn the blower to high. If you see mist that smells/taste like coolant, than the core is leaking. If you seen no mist or anything, than the leak is coming from somewhere else.

Also, have you checked your coolant level lately?

also dont ever use stop leak products unless you dont care about the engine coolant passages plugging

Wet floor under the gas pedal is not very likely to be coming from the heater core. More than likely you are leaking through the driver'* door panel water shield.

Test your system like Mike suggested. Leaking fluid from the heater core has a very definite sweet smell to it.

Do you have a sunroof?

Don't EVER put something in the coolant system to stop leaks. It blocks smaller coolant passages and you will end up with a bigger problem on your hands.

Found that the leak is NOT the heater core and not coolant. Plain water is coming in from somewhere. Had windshield glass supplier check front windshield and no leak from there. They will check front area under hood firewall area Wednesday, but that doesn't sound like a leak source. I don't understand the suggested area for the door leak, but I'm still looking. Thank you folks.

Has a electric window actuator been replaced or any other reason to remove the interior door panel?If so, that is a good place to start troubleshooting where the water may be entering. Do some searches here for water on the floor of Bonnevilles, and you will find lots of people with likely problems and the fixes.

Yep, the window operators have all been replaced at one time or other. I'll check under the driver door panel at the next rain or maybe using the hose after freezing weather has passed. Thanks.

The watershield is a translucent sheet of plastic stuck to the door inner sheet metal with butyl tape. The door is a "wet" system which means it is designed to control the flow of water, rather than keep water out. The watershield prevents water from coming into the vehicle, and it forces water to flow out the drain holes in the bottom. If the butyl tape dries out and the plastic seperates from the sheet metal water runs into the interior of the vehicle. You can test it with a hose, but I doubt you will see the water flow. Best to remove the door trim panel and examine the watershield to ensure it is properly sealed to the sheet metal.