How can I confirm for sure the head gasket is gone? Leave it for another week and see if it fills with water/coolant again?

The coolant was down about 1/4" but I thought was due to the cold temperature. The coolant is clear in the plastic tank.

I did smell the exhaust and there was no antifreeze smell. That big cloud of white smoke reminded me of a Lincoln that blew a head gasket and you could smell the antifreeze in the exhaust.

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1989 420 SEL