Vent above rear window
 

I have read on this forum that the slots above the rear window glass on 911's originally had foam rubber in behind them. The purpose ? Sound deadening , filter ? I have unzipped the headliner and found the channel described in a thread I read. The are no remnants of anything in my car of anything. Iam just a bit reluctant to put a moisture holding sponge like substance in there .Where I live can be quite wet driving in rain the airflow would keep water out but sitting in rain ?? Any thoughts ?

In case you didn't see it search for threads under my username I think I started one a while back describing what I did. I suspect you may have found it already.

The factory used open cell foam in there, so there likely isn't any reason you shouldn't do the same. I'm sure less rain will get in WITH the foam than without.

no rain should get in there, unless you are literally in a hurricane. if you are geting water inside it is because the rubber window seal itself is leaking.

You can get water in without a hurricane. Grab your garden hose and spray!
The answer? Point the hose towards the rear.

Your thread was the one I read, I guess its not so much water getting in , I have not had that happen even without foam rubber in place. My concern would be the foam getting wet and holding the moisture like a sponge and starting rust.

how often have people seen rust there?

not a biggie based on posts I've seen here

When I replaced the headliner on my car, I tore out the old crumbling foam and found no rust at all. In fact I replacef the old foam with closed cell foam above glued in and later on held up by the headliiner stays. I figure the closed cell foam may cut down on the heat from the sun overhead.

Will cut down on airflow... which is it's purpose.

It is NOT supposed to be insulation.

cut down how about CUT OFF airflow.

I filled the vent with some inflated rubber. It worked well and cut the noise to the interior way down. I posted my work here.