I have an automatic 86 Vanagon w. air. Yesterday, I was driving along and
my coolant tempature gage light went off. I checked my coolant expansion
tank and it was empty. I refilled it and light went off and everything was
fine. Today , I checked the coolant and it seemed lower than when I filled
it, but not as low as yesterday.  There seems to be no puddles of coolant
forming under the car or visible leaking.  Could this be a fluke, bad water
pump or the dreaded head gasket. Thank you for any advice.