Went in leaking coolant looking for a diagnosis and wanted and oil change, turns out my head gasket is blown so they said, later on he didn't realize it but he said it might be blown. This has happened before, as soon as you mention you overheated once just a little the diagnosis is needing a new head gasket. even if there's no white smoke, oil in coolant, coolant in oil, loss of power or all of the other symptoms of a blown head gasket. It's an expensive repair and one they seem to love suggesting you need done. They found I am leaking coolant from my water pump which seems like a reasonable diagnosis. Your service guy needs a little lesson in tact in letting people know they're car needs a lot of work too.