I recently purchased a 2006 330i. She's a beautiful ride, but has recently started having issues. Driving home the other night my engine overheating indicator light came on. After that the car wouldn't accelerate past 3200rpm. This morning I checked my coolant level and it was just about bone dry. This is after I just filled it up about a month ago. I'm not seeing any evidence of a leak either. What could be the issue??