Purpose of chassis vents on rear door jam?

[lordoeuf]

My '99 XJ has this grill which looks like a vent on the back seat door jam. You see it when you open the doors and it is on both rear door jams. The grills are fanned down so that rain water doesn't get into the cavity behind the grill. There are also these rubber flaps behind each grill of the vent panel. What is the purpose of these vents?

If you unscrew the vent, you see a cavety which ultimately leads to the rockers below. Under normal use I don't imagine water getting into this cavity from these vents, but if you cross a deep enough stream, I can see water getting into this cavity from these vents. I was considering sealing up these vents, but wanted to know their purpose first. Thanks!

 

[Tim_MN]

All the vehicles that I have owned had some sort of vents for passenger compartment.

Wondering why you think the vent needs to be sealed ? Pour in some water, it will likely get your shoes wet. If you are crossing waters that deep, you have bigger worries than vents that drain to the rockers.

 

[lordoeuf]

Not just for streams, but when I wash the car I also spray water in that area. My kids have also spilled water on these vents in the past. Some water does get into the unibody cavity usually from the bottom most portion of the vent. Water trapped in this cavity will encourage rust. There is already some rust in this cavity, but not a whole lot.

So what is the vent for? The rubber flaps are oriented in such a way that to allow air to flow from inside the cavity to the outside.

 

[RCP Phx]

It's just a air pressure relief for when the doors slams shut and when "on" outside air fan setting.

 

[Black1990jeep]

The rocker have drains if that vent takes in water and it dont drain, then there are problems. clear the rocker drains!