Usually head gasket to coolant breach puts combustion gas into coolant and can actually blow the lid.

How much fluid did you have to add to float the float? It usually takes under a pint to go from float resting at the bottom to full.

My wife's x has a minor coolant leak i have to add weekly but it never drips. It will evaporate before it comes out.

You could easily have a leak that just blew away while driving and never drips.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)