Well, it sure looks like it was a bubble! Now I have to figure out where a gallon of coolant went over the past few months ... or maybe it just wasn't all the way full when I bought it.

Thanks guys!

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Finn John -- Albany, Ore.
www.offbeatoregon.com
76 Merc 300D, sky-blue, *86k, for driving
84 Jaguar XJ6, black, 245k, for restoring someday
71 Merc 408, 2.3 petrol 4, Avon caravan conversion (UK), RHD