Interesting.  So maybe going down the road, higher engine rpms, the coolant
is moving fast enough through the tank to pump enough of it through the
engine along with some air, to keep it cool but once the engine is warm, at
idle or stop and go driving, the water pump is just getting too much air or
little to no coolant.  And also the coolant/air mixture would separate on
the other side of the engine and mostly air would end up at the heater
core.

Good spotting that Mark.  I don't know where you saw a picture of Jim's
tank... an example of one of the times it would be nice to have a list that
could handle attachments.
Edward

On Thu, Dec 10, 2015 at 4:53 PM, vw_van_fan_Mark <madvws@cox.net> wrote:

> Jim, I'm not saying that will fix all your problems but it is a place to
> start.
>
> All Vanagon cooling systems use the top of the tank as the collection
> point for air and then it gets pushed out through the cap over time. The
> water pump is supposed to draw coolant from the bottom of the tank. The
> way it is now the waterpump is drawing from the top of your tank, where
> any air would be, the opposite of how VW intended.
>