I also have cold fresh air leaking into my van.  It is particularly
noticeable somewhere on the driver's side of the dashboard, but this is
possibly because I can feel the air flow there while I am driving.

In an effort to resolve this air leak, I removed the top outer front grill
and securely fastened a  piece of cardboard (properly sized, cut, and taped)
over the plastic wire mesh screen that covers the air intake duct.  This
should have stopped all fresh air from entering the heater box enclosure.

Is there a second air intake duct, possibly coming from the bottom front
outer grill?
A search of my Bentley has failed to find a diagram of the air intake flow
passages.  Did I miss something?

The air ducts going to the outer dash fresh air vents are tight as are the
door flap seals in those vents.  Please note that this is an 86 van with
only fresh (nonheated) air coming from those vents.  (Heated air from those
vents started in 1987.)

Anyone have an idea of where my air leak is occuring?

Budd Premack
86 Syncro, 84 GL, 73 Super
Minneapolis, MN (Land of Frozen Waters) AND COLD TOES TOO!