Got back from a 16-day trip, started my 2007 A4 quattro 2.0T, backed out of the garage, got the flashing red coolant light on the dash. Stopped the car, looked at the tank -- no coolant. Looked at the garage floor -- no coolant or orange stains. Added over a pint to bring it back up to spec. But what happened to it? Supposedly sealed for life! Bill