If you're lucky, you just have a bad expansion tank cap or the hose that goes between it and the overflow tank.  It allows the fluid to expand out, but not draw back in.
I just replaced one on a '90 Carat that was doing that.

GregM

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of John Rodgers
Sent: Thursday, December 08, 2016 9:49 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Coolant light 2.1L WBX

Driving down the road, all needles where they should be, red coolant light comes on. Stop the car, check the fill/overflow tank. It's up to the top mark. Next , empty the baggage area, raise the engine hatch lid. Removed the expansion tank top, found coolant to be below the sensing prongs on the sensor, thus the flashing red light. Topped off the tank to get home. No more red light. It was dark, so must wait to tomorrow when it cools off to see where the coolant  went. But I could see there were no coolant leaks.
So the question is - where did the coolant go.

Ideas??

John