rain leak

I have a 91 G A, last night when I got home, there was a puddle about an inch high on the passenger side floor, and in the back seat floor, also under the passenger seat. I felt around where the heat comes out and it wasnt wet at all, theres no noticeable wetness anywhere else, just on the ground. What could be the problem?

The water is leak in through the air plenum from the outside. There is a plastic cover over the windshield (Trim). The seal is allowing water to seep in. The area is under the wiper blade. Remove the cover and clean the glass and apply a bead of sealant and re-install the cover and let the sealant dry.

Good luck

the other common problem with Grand Am's is the seam in the floorboard behind where the rack and pinion mounts splits from stress and will start to leak. As long as the fluid is just water, it's either the heater box like Flyboy said or the seam I mentioned. If it's coolant, you have a bad heater core.

I had a water leak but I fixed it after much frustration. I actually went out in the rain to see where the leak was coming in. I tore up all the carpet and saw that it was leaking through the firewall somewhere. I used rubber undercaot to seal everything but what it ended up being was a golf ball sized cavity under the plenum allowing water to seap through. The factory sealant to close the sheet metal had failed. That's all I know about this subject. Good Luck