MY 2008, built 03 2008 51700 Miles. N54, cost 1238 no warranty.
This turned out to be an interesting ordeal.
1. Water Pump Fails
2. Replaced by Wichita BMW
3. Driving home the Oil Temperature gage goes to 250 after 5 minuts of driving and the oil level indicator says inactive. The Oil Temperature gage dropped down to 200 in about 2 seconds as I was watching it, and then the Oil level gage showed the right amount of oil. No indication of anything wrong.
4. Got home parked the car came back out after an hour and had coolant all over the garage floor.
5. Tow truck came the next morning and the battery was dead. Had to push the car out of the garage.
6. BMW replaced the water pump the next day and said that apparently the first water pump replacement shorted internally as I was driving down the road causing the bizzare gauge malfunctions and drained the battery overnight.
7. Alls well that ends well, but just be aware that if the pump dies it can cause some strange things to happen.
These cars will cause you to fret, and I was cursing it for a while but in the end they are too much fun to give up.