The air vents in the rear door jamb (top). Some years had a round "hogs hair" type filter on the backside of the vent - my '72 has them.

Anyone know what years didn't have them? What other years did have them?

Not one of those things a concours judge would ever check, but curious.

My '74 2.0L has them.

Model year '70 & '71 did not have them. My sixes don't. Johnson book got that about right.

Don

A bit of a highjack, but......which way does the air flow to vent what?
Assuming the air flows from the cabin to the rear wheel house, why filter the air? Someone lead me to understanding! ( Maybe this belongs in the "mystery" thread)

I do know that the door vent is an exit vent for the cabin. But that is a good question. Why was it filtered from the interior. I also know that it saves a ton of weight not having them on the early cars.
And Pat, you should be checking them on your concours rounds. Another place to stick your finger.

Don

My understanding is the vents reduce the pressure in the cabin while closing the doors with the windows rolled up. They make the doors easier to close.

I don't know for sure why they went to the filter on later cars.

My '70 /6 doesn't have them.

True, pressure relief is part of the design. Been around for half century or more. More importantly, it allows for the fresh air to come in the grille on the cowl and exit through those vents. Flow through.

Don

My 76 has them.

Porsche added the filters to capture water so the air ducts would rust quicker.

...and I thought they were smoke filters.

Don

They are Don, when you don't change your fuel lines often enough.

Think I have to agree with the reason for the vents - makes it easier to close the doors without blowing the roof off.

But.....why filter the air LEAVING the cabin? Is it hooked up somehow to the engine intake system, so that unburned methane (farts in the cabin) can be recycled?

Seriously, where does the air exit from these things?

Sixerdon - can't check them for concours because you'd have to remove the vent cap - a no-no. Though it would be a great thing for a tie breaker.

BTW, to show how anal I am, I run my filters through a diswashing cycle every couple of year (not including the heat dry cycle). I'll be the first to admit it's crazy, but has anyone tried to source these parts? It also gives me the opportunity to clean the channels.

I know these were used from mid '72 thru '74, but what about the 75/76's?

as I said they are present on 75-76 cars.

There is a port in the cabin targa pillar and then it routes to the fender port. Why there is a filter, I don't know other than they do clog with dirt and crap and will fill with water so the rust cycle begins....

Shine a flashlite into them and just look closely Pat as you can see in there if they are filtered or not.

How many points to deduct?

my '70 914-4 had 'em ...
Andy

simple, when driving, the air flowing by the door (gap) creates underpressure.
that, together with the positive pressure from the cowl air-inlet, creates an air circulation through the car.
the air exits through the vent-hole and out the door gap.

the filter is for those times when you don't drive fast. like sitting in traffic on a windy day, air (and dust) would be pushed inside the cabin through the vents ...

and yes, my '70 914-4 had them !!!
Andy

Gee thanks Andy! You just destroyed a pattern! Looked like the early cars (70-mid '72) didn't have them & all the rest did. Now you have to come up with this 1970 that had them.

So why have I seen so many early cars through the years without the filter? Jeez, is anything straightforward with these cars?
Pat

Yes, they all rust!

If most early cars don't have them ( I know sixes I have owned did not), it could be that someone added them to Andy's car at some time in the last 36 years ( or removed them from my sixes, I guess).

The filters are more of a bug screen. Keeps wasps from nesting where you cannot get at them.

that certainly is a possibility ...

my car had many PO's ...
Andy

Its my opinion that these were added to help demist the rear screen

What if you have the rear window de-fogger (de-mister)??