There are some BMW parts which exhibit failure modes with frustrating regularity. The 4.4L engine has the radiator/expansion tank issue at 70k miles like clockwork. My E38's radiator failed at 71k and the expansion tank at 140k. I had an appt the next day to have it replaced because I knew it was reaching the 140k mark. It failed a day early.
Obviously the oil separator is a known issue. My service manager knew what had happened before I got three words out. "Oil leak" was enough to tell him I had joined the long line of oil separator clients waiting for their cars.
My E24 was a dream to drive, but it was a maintenance headache. My E39 was flawless except for a sunroof seal which they fixed under CPO warranty. My E38 was a monthly failure machine, but it was an incredible car to drive. My E53 was flawless through 100k, but it's been costly to keep up with the worn parts for the past year. My Z4 is too new to have issues. I guess I need to get to the point where I can trade vehicles in before the CPO runs out.
