1987 Honda Accord Sun/Moon Roof Drains

There are no drains in the floor. If there were, snow, rain, and mice could get in. What you likely were told about is the AC condensate drain. The cold evaporator in the dash removes humidity from the air as it cools it. That water condenses and drips into a pan, then onto the ground through a tube through the firewall. That tube can become blocked, then the water backs up until it spills onto the floor, usually on the passenger front floor.

The AC also runs in defrost mode to remove that humidity so it doesn't condense on the cold windshield and cause fogging. Look under the hood on the passenger side of the firewall for a 4" rubber hose with a 90 degree bend in it, hanging down behind the engine. Squeeze the end of it to open it up. If nothing comes out, there's a wire ring you can squeeze to pull the soft hose off, then carefully stick a pencil into the tube to dislodge any debris.

OHHH! Those aren't "floor drains", as in meant to drain water from the floor. Those are sunroof drains and there's typically two or four of them exiting through the floor in different places. Most commonly the debris collects up on top and water may sneak in by dripping from the window glass. Even if all of the tubes become blocked down at the bottom, water will just back in them up to the glass, then run over and into the car. What makes it confusing is that water may run on top of the headliner to a low point where it runs down and is first seen on the floor.

Open the window glass, then look around the rubber seal for the drain holes. Start by poking around in them to see if they're blocked. You might also try using a small wet / dry vacuum cleaner to pull any debris out that washed down the tubes. The manufacturers usually make the tubes wider near the bottom, not smaller, so if something makes its way down that far, it will wash out rather than get wedged in there. If you think there's something closer to the bottom, use a long piece of stiff wire to run down the tube. Wire from a wire feed welder works well. It's hard to kink and is very flexible.

Sorry. That was my fault for overlooking "SUN/MOON ROOF DRAINS". You'd think I would have seen that the first time.