Oil Seperator ***
 

Ok, after reading all the terrible experiences about the oil seperator failing in cold regions. Here are my questions:
- Should we replace it before it fails? Or wait until problems occur?
- How much is the updated part?
- What to do to prevent it from failing?

If you have more than 60,000 miles on the vehicle, it seems to me like a reasonable preventative maintenance item. You can actually clean it out, you don't have to replace it, but I am not sure if it is worth the trouble. The lines have to be cleaned out or replaced as well. If you live in a cold climate, and frequently have short trips that don't really get the oil hot, then it is even more worthwhile. If you live in Florida, for example, I would forget about it.

Real OEM lists the valve at around $65. On the 3.0, BMW suggests removing the intake manifold to get to it but there are DIY articles on the web that suggest that is not necessary, you can get it out without taking the manifold off.

If you have a later model X5, with the heated or insulated lines, it is less likely to happen, but still can. In that case, I am not sure there is much point in replacing the valve as a risk-management plan.

It seems like the 4.4 has a number of issues like rough cold start up and the oil issue, seems like the 3.0 has less issues.