I have a 2000 Mitsubishi Eclipse GT that collects alot of water on the driver’s floorboard all the way to the back seat. It seams to be sealed good but since we bought it new I don’t know if it leaks because of something the previous owner did or maybe it’s a common problem, like how the dash cracks into pieces on those things. Thanks, Bill
My first thought is that the water drain below the windshield (where the wipers attach) could be plugged up with leaves or other such crud. One bit of confusion: You say you bought it new, but you refer to a previous owner. Can you clarify?
Check the ventilation system drain tube. This tube is on the firewall, low on the passenger side. You may have to get under the car to find it. Do not crawl under a car supported only be a jack.
As noted the drain from the vents in front of the windscreen is a common problem. The A/C is also possible source. One additional common problem is the sun roof if you have one.
A not too likely problem could be a rusted out area in the trunk or under the seats allowing water in.