I have a 93 civic coupe, i noticed lately that everytime it rains, i have a frigging lake inside my car on the floors on both passenger and drivers sides. I parked the car in the garage vacumed the water out and pulled it out into the driveway oevrnight. It rained all night and in the morning i had a puddle again inside the car. I checked underneath the car, the floors are solid, no rust, the door seals are fine, and the seal around the windshiled is fine (no rust). there are no fluids leaking from the engine and cooling system is fine. Does anyone know if it is possible that water could come in from a special spot somewhere near the firewall below the windshield or in the vent intake???

 

Have your friend spray the car with a hose while you sit inside. This should help you locate the leak.

 

I had the same problem and i fixed it. In your trunk if you pull the carpet up either on your lef side or right side of your trunk there is a vent that circulate the air for your trunk. In my car (95 with moon roof) i have the vent on the left side of my car plus a plastic tube that drain water for my moon roof. Check to see if your tube is disconnnect from the socket if so reconnect it. If this isnt the case then check your side vents in your trunk. Sometimes there is a leak from the outside into the vent what i suggest you do is get some kind of water resistant silcon and apply it on the side of the vents that should do the job. To find out if the vent is the problem take a bucket of water and dump it in the the back of the car and see if there a puddle coming from the vent down to the bottom.

 

the leak is in the front. near the firewall. it could just be a bad or missing grommet.