Congrats, Jack, though it looks like yours will be a project vehicle for awhile yet. In the last year, I have found lots of helpful info here. Though the search tool isn't perfect, you seem to be finding what you need. At your age and mileage, could be just about anything, though leaky steering rack and CV boot issues seem to occur. Is yours an auto or manual tranny? If automatic transmission, opportunities for issues there, too.

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2006 X5 3.0 6-spd w/Evo UUC ssk
sport/premium pkgs
born Valentine's Day, 2006.