One problem related to radiator has been reported for the 2008 BMW X3. The most recently reported issues are listed below.
I noticed water on the garage floor about a week ago and that the coolant was low. I took it to BMW dealer expecting a radiator leak. I was told that all 4 aluminum support bolts had been sheared and that the engine was resting on the water pump causing the leak. The solution, while covered by my extended warranty, is still costing me $50 deductible and another $200 or so to flush and replace the coolant (which was caused by the water pump damage). If I didn't have the warranty and was forced to pay for the labor, bolts, support brackets and a water pump - I would be even more irate that BMW hasn't issued a recall on this well known issue.