Two problems related to coolant leaking have been reported for the 2009 BMW X5. The most recently reported issues are listed below.
Car began to overheat while driving on highway, exited highway to city street, then the alert for low coolant came on. Immediately found a place to park to keep engine from being compromised. Allowed to cool, opened reservoir and coolant was low. Added one gallon of approved coolant. Drove for 5 miles. Car sat for several hours. Started car, alert came back on. Checked beneath vehicle, all of the coolant leaked onto the ground.
Critical failure/ crack of the coolant reserve tank. No prior indication of leak. Tank split open and lost all coolant when parked. Searched online and see a large number of people have reported same problem. Potential for engine damage significant. Non dealer cost to replace $400 and read other have had dealer replacement cost $800.