Hi - I bought a new car 2 years ago, and for the past few months, I’ve noticed sounds of water sloshing around under the passenger side front floorboard. It’s usually when I stop or turn, and definitely louder when it rains. There is no wetness inside the car. Should I be worried? (I have looked, and there are no water bottles stuck under the seat.)
Yes, you should be worried. Peel the carpet back and see if anything’s wet under there.
And if you don’t find water under the carpet, check inside the doors.
Another possibility is water in the HVAC system.
The HVAC and the doors have drains, and if they’re clogged up water will be retained. Clogged sunroof drains can also allow water into the car.
Wherever it’s coming from, you have to find the water and get rid of it. Mold, mildew, and rust will develop if the water remains.
One long shot. Did you have “rust proofing” done to the car? Rust prevention after the car leaves the factory can cause a bigger problem than the rust you would get without after manufacture treatment. The after manufacturer products tend to block up drains that are needed to protect your car.