Two problems related to engine belts and pulleys have been reported for the 2008 BMW X5. The most recently reported issues are listed below.
The engine idler pulley bolt broken.
I was left stranded on the 695 baltimore beltway after my vehicle displayed an over-heating signal in my dash. A few seconds later, the engine shut down and a red "engine overheated" signal appeared on my dash and I was only able to drive less than 5 miles an hour to move to safety (in the midst of many cars flying by me doing well over 65 mph). Very scary situation. The other scary situation is that I am 3,000 miles out of warranty for this issue and I feel that because my vehicle is not the only reported incident of this type, BMW should repair the problem at no cost to me. A part such as this should not fail at 53000 miles.