One problem related to radiator has been reported for the 2009 Mini Cooper. The most recently reported issues are listed below.
While traveling on a highway at @ 55mph, the coolant temperature warning light illuminated yellow and then red on my 2009 Mini Cooper. I stopped the vehicle and observed that the clips which secured the lower radiator hose in place had broken and the radiator hose was hanging horizonally across the front of the vehicle, dragging along the ground. A hole had been worn through the hose and the coolant had leaked out. After having the vehicle towed home ($285), I purchased a new radiator hose and clips from the Mini dealership ($160) and had it installed by my mechanic ($100). I also lost a 1/2 day of work. A total loss of over $600. Because of poor design and/or inferior materials internet research shows that this is a common Mini Cooper problem. I did not hit anything which would cause this issue, despite Mini Cooper's attempts to place blame on the driver's who experience this issue. If Mini Cooper would properly address this issue and remedy the situation, it would spare countless driver's from being stranded on the side and the expense of fixing what should have been remedied by a service bulletin or recall.