Sounds logical. Outside temp of -5. Subtract for 65 mph and windchill. I had heat, but noticeably cooler to the bare hand.  Never did warm up the van in 50 miles. I thought maybe this was par for such a cold night.
I'll order a thermostat. 
FWIW, upon restart the eng sounded and felt 100% normal-just heated quickly.  This leads me to believe valves and other biggies were spared and maybe it is as you suggest. 
Should the coolant mix be "thicker" than 50/50 in extreme cold?
Thanks for the response,
Jay
I'm trying to clear garage space to bring her in. It's too darn cold to do anything outside. See also next post. J
    --
    
    Had a similar situation with our Jetta last winter.  It was a freeze up.  I had changed coolant earlier in the year, apparently got the mix wrong and the coolant froze in one of the hoses plugging the flow.  Big time overheat when the temp was 5 deg outside.  Took over an hour for the plug to thaw, then back to normal.  Another possibility is a stuck thermostat.  The spring in the thermostat will theoretically pull it closed tighter and tighter as the temperature drops.  Maybe tight enough to stick. Either of these blocked-flow possibilities would produce another effect: no heat. Were you getting heat?
    Gary

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