One problem related to crankcase (pcv) has been reported for the 2003 BMW X5. The most recently reported issues are listed below.
Crankcase vent valve froze & blew off oil cap. Oil all over engine. Replaced crankcase vent value, w/ non original, & all hoses. Removed & cleaned out dipstick tube, distribution piece. Removed lower engine splash pan & stiffening plate. De-greased top & bottom of engine compartment. There is a service bulletin about this propensity for the crankcase to freeze. This is unacceptable in cold weather states. The auto is sold in the cold weather states regardless.