I have a 97 grand prix. When it rains water leaks in the front passenger floor board. My a/c doesn't work. When coolent was poured into it it also leaked all in the floor.

On the early 2000 model Grand Prix the issue with the water leaking into the passenger floor board is usually the seal that has come off near the blower motor, this seal is easily able to be replaced and is inexpensive right from GM. You can remove you wiper blades and the plastic coweling in front of the widshield then look down inside where the intake is for this blower motor and you should see the seal just laying there or maybe hanging off. The purpose of this seal is to divert rain water that runs down the windshield and into this intake area. Replace this seal and it should take care of the issue.

If this isn't the issue some of these cars had an issue with the windshield not having enough adheasive installed on the lower portion of the windshield and allowing rain water to be driven in between the window and the dash, the water then runs down the firewall behind the dash and corrodes wiring. A friend of mine had this issue on his pontiac and had to had the entire ECM wiring replaced and the window resealed.

Ac hose leak?
leaking heater core?

Hint: it leaks when it RAINS

If it were related to the heater core or the AC drain, it would be leaking when it is not raining also, so those diagnoses are not logical.

The grand prix has a long history of floor leaks from seal failures around the air intake under the windshield cowling, where RAIN water runs in.

I have a 1997 Toyota Camry. Water was collecting on the front PASSENGER floor after a rain. I opened my sunroof and found the front drainage holes (about 1/8" diameter) in the corners of the track sunroof track. They looked clear. I poured a bottle of water in track and watched the result. Sure enough, water started dripping from the right ride of the glove box on to the floor. I started tearing out the interior panels to trace the leak. What I found is that if I poured the bottle of water REALLY slow into the sunroof hole = no leaks. But if I pour it too fast the small 1/8" hole cannot keep up and the track overflows! THAT is where the leak comes from in my car! If water overflows the track, then it makes its way down the column trim, around the glove box and on to the floor.

So I need to help the 1/8" sunroof hole drain faster. I took some 18AWG TFFN electrical wire and jammed it into the hole to help clean it out. I then removed the black plastic mud flap behind my front tire and blew out all of the leaves and rotted debris that where behind that flap. It was packed with junk! I poured more into the 1/8" hole and it seemed to drain quicker.

I hope this information helps others.

A leaking windscreen,door seal or window seal. Run a garden hose over your car and use baby powder to pin point where the water is in running from.

sounds like your heater core is leaking

Check the bottom of the door for clogged drain holes. Could also be a weatherstrip seal leak around the door opening. Worst case there could be a leak around the windshield gasket.

possibly leaves or other trash way down under grille at bottom of windshield

pull your carpet up near the leak area and look for muddy body seams. it is possible one of the factory body seams are leaking- possibly in the cowl(under wipers) area, especially if it leaks when the car is sitting. there will be dirt/mud around the seams that are leaking. also you can check door seals by running the car on HIGH DEFROST with all doors and windows closed. spray around with a 50/50 soapy water solution. obviously bubbles will form around your leak.

Is it water or coolant, if its coolant need to replace heater core. If its water could be door weatherstrip problem or windshield leaking . also can have someone spray water on car and you sit inside and look for water leaks.

could be that when it rains or is wet out that water is leaking into your car under the hood under the vent by the windshield wipers on the passenger side and instead of being filtered out its going into the car on the passenger side floor. (check to see if this is wet after a heavy rainfall) and causing a short and rusting it out. this happened with my 2002 grand prix just this year. I got a water resistor for like $3.50 from a local pontiac dealership/parts store and put it in. Its easy to install and it poured out today and my car didnt leak at all.