Brent, with warmer temperatures, this is normal.  When the engine is first shut
off, the coolant temp in the engine itself rapidly increases for a short period
as heat is absorbed from the heads & cylinders, the liquid coolant expands, and
the pressure valve in the coolant reservoir tank opens and allows coolant into
the overflow tank.  Within less than a minute, the system begins to cool off
sufficiently that coolant begins to be returned back to the system from the
overflow tank.  I have been experimenting with operating a system with no
coolant pressure whatever, using an overflow tank mounted on the left rear side
of the van where I can keep an eye on it in the mirror.  I notice that on
shutdown of a hot engine, the coolant level rises rapidly, then begins to drop.
I have no restriction (pressure valve) between the coolant reservoir and the
overflow tank.  I simply removed the valve from the cap.  I realize that I have
lowered the boiling point of the system, and that it may not be possible to run
it this way through the summer, or at higher altitudes, but it's just an
experiment.  So far, it has worked OK, though, and if it does perform
satisfactorily at higher ambient temperatures, running an unpressurized cooling
system does have some potential advantages, especially in the waterboxer motor.
I'm at about 850 feet altitude, in Iowa, by the way.

Brent Christensen wrote:

> After running around town last week in my Syncro Westy, I noticed that right
> after I shut off the engine, I heard gurgling noises from the cooling
> system.  I quickly ran to the back, lifted the hatch and noticed that
> coolant seemed to be bubbling into the expansion tank.  It stopped after
> about 45 seconds, and as I recall the level in the over flow tank appeared
> to be normal.  This is the only time this has happened, and it hasn't
> happened since.  Is this normal, or do I need to "burp" the cooling system?
> Could it be a sticky thermostat?
>
> PS - the cooling system, engine, hoses, H20 pump were replace about 25,000
> miles ago.
>
> Thanks
>
> Brent Christensen
> '89 Syncro Westy "Klaus"