It sounds like you're talking about the Vanos oil supply line. Is it the #15 hose in these pics (may not be the exact same as your car depending on engine)?
I replaced this last week on our X3 since it was leaking on the lower side of the line near the oil filter housing. Make sure to replace the copper washers as well.
BMWs currently in the garage: VF570 E46 M3, E46 XI Touring, E83 X3 "M" retrofit
Last edited by chagrin; 12-15-2012 at 02:30 PM.