We just went through a bit of a storm where we got over 9 inches of rain in two days. My wife was doing her usual 60 mile round trip commute.

Yesterday we went to get in the car and the passengers floor had a puddle of water.

My first thought was a drain plug clogged in the engine bay area but couldn't find one. On my Jaguar it is called the duckbill drain that allows the outside vents to drain water. I didn't see any on the Volvo.

Next I crawled under the car and saw that there was a rubber sealing plug missing on the chassis under the passenger floor boards. There are holes for three and one was missing.

Our car parks in the driveway on a slant. I pulled the rear plug and water poured out of the hole.

My guess is that sitting on the slant, the water just sat in there like a swimming pool and eventually found its way into the inside floor board. One sealing plug is solid and the other plug has a hole in the middle with slots emanating around the hole. I guess the slots allow it to be flexible.

The drivers side had no sealing plugs and no water inside on the floor board. I guess not having that rear solid plug allowed all water to egress.

I have friends that say using such plugs keeps moisture in and allows rust to start. Other people feel that plugs keep water out and you don't need to worry about rust.

Should I go buy the plugs or keep open holes that the air can flow through and dry out the stamped chassis.

The next idea would be clogged sunroof drains and / or clogged AC tubes.