OK... I vote for George Chapman's explanation about the rear vents "allowing
a slight release of pressure within the vehicle when swinging the door
closed." With that foam insert in there, they sure can't do much else. But I
really wrote because in reading the postings on this topic, I think there's
some confusion about "rear vents"- I don't think you all are discussing the
same vents...

Those with older WC and air-cooled vans have one set of vents which connect
the engine compartment to the outside world. When people refer to the vents
"vital for engine cooling" or "left-overs from air-cooled" engines, these
are the ones they are speaking of. The opening faces the front of the
vehicle and based on it's form would seem to be intended to scoop air into
the vehicle when moving.

On newer WC Vanagons - I don't know the cut-off year exactly - perhaps '87
or '88 (? I say that because there's a syncro locally w/o the vents, and
syncro's started in '86, right?) - there is a second set of "rear vents" -
these are actually in the window frame (the rear windows shorter on these
models) - in front of the "engine vents". They are stuffed with
dust-filter-type foam and connect the interior of the vehicle to the outside
world. The openings on these vents face the rear of the vehicle, so it would
seem that these are not for scooping air into the vehicle, but for
extracting it. Except when driving in reverse, of course. So...

Older Vanagon = 1 set of "rear engine vents", full length rear window
Newer Vanagon = 1 set of "rear engine vents", 1 set of "rear interior
vents", shorter rear window

Doug Fitz-Randolph
Yarmouth, ME
dfrandolph@talkam.net
'90 Syncro