paul:

van may or may not have suffered serious overheating. when expansion tank
emptied, the electrodes of the coolant level warning light switch would
have been uncovered, causing the rapid rise of the tempertaure gauge and
flashing led. once air is on top of coolant it tends to stay there, just
like any bubble, so once expansion tank is empty, high pressure air is
happy to "float" on top of coolant as a pretty stable bubble.

agree with previous post that bleeding system to purge as much air as
possible would be reasonable first course of action.

here is a novel bleeding procedure. i'm having technical trouble starting
new threads, but have no trouble posting responses. so what follows would
normally be the start of a new thread, and is not to be considered a tried
and true method. in fact, i am hoping to get some feeback on this idea:

barely crack radiator bleed screw. go for a drive: up hill, downhill, bank
left, bank right, and so on. close bleeder screw. top off refill tank.
repeat as necessary, with heater valves open or closed.

i tried this with success recently, and found long 10% - 15% grade, and
high rpms, very helpful. lost about a cup or so of coolant in the process.
i drove for maybe 1/2 hour, stopping to make sure bleeder screw was
cracked open enough, but that there wasn't an excessive coolant loss.

dan