I agree with JCL and others that as part of regular maintainance you should check and clean/inspect the ccv parts. The only trouble is that this includes a LNG list of items; dipstick tube, oil sep, oil sep hoses, bottom oil sep hose, rear ccv on the intake manifold, intake manifold ccv hose.

(I'm speaking in terms of the M54 V8 engine.). There are many narrow spots in the system that can become clogged with the sludge. If you only check the top oil sep hoses and the oil sep itself you may miss a buildup somewhere else.

As for the pressure relief idea, it's a great and simple one. Why didn't BMW think of it, or at least offer one as a fix.???
Someone else on the board suggested to clip one of the o-rings on the top of the dipstick, giving a weaker seal and providing a pressure relief point. On Gm and ford engines, this sludge problem can happen but typically the pressure (and oil) shoot out the dipstick tube or pcv hoses, which is a helluva lot better than valve covers and hydrolock failures.

I had two sets of valve cover gaskets blow back to back within a month one winter. The second time was because the bottom oil sep hose and return tube were not cleaned (thanks BMW of Rockford, il). BMW lost a lot of integrity points with this problem. But, faaaack, the X5 looks hot! And when something looks hot, we put up with more sht.

Oil separator and window regulators are probably the two worst designed pieces on the car.......crap engineering

I hear you, and understand your frustration. What I don't understand is why some owners have so many problems, while with my last six BMWs (dating from a 1994 318i) I have driven in lots of cold weather, down to -30C, and have never had a problem with any oil separator. I have also never failed a single window regulator. :dunno:

I agree JCL...no window problems on mine but a friend with an '04 has had to change out 3 regulators already. He drives a lot with the windows all the way down in the summer whereas I never do. I was never too happy with that rattle the door/window made when you closed it with the windows down so I don't do it- I'm convinced that that is why his went.
Same for oil separator...no problems or gunk here so far (touch wood) and I am one of the park outside/short winter trip 'offenders' - no problems either with my E46 M3 and my previous E46 330Ci. Don't know why I have escaped...although Boston doesn't get too cold in the winter .....relatively speaking.

To add to this thread, if the valve freezes it can ehiter freeze open or closed. And pressure relief valves on the spark plugs only cover one mode of failure. (which would never work imo as they would let out compression or not be effective enough to release that much viscous liquid at that speed to save the rods, and would cause coil fitment issues) The other mode of failure pressurizes the crankcase and blows the oil out of the weakest link, usually the valve cover gasket. amacman's idea is more plausible as the CCV system is a very low pressure system usually (negative pressure, but still) The valve that would let pressure out would become the fail point for oil blow out while the in valve could possibly let in enough air to prevent it from sucking oil from the crankcase...

But as usual I agree more-so with JCL that it is more important to properly operate and maintain the vehicle than to accommodate for preventable failures. And I also agree with a point he made on a previous thread that most window regulator failures are likely caused by slamming the doors closed with the window down, as when it is down it isn't fully supported by the guide tracks. If you are able to adopt the practice of rolling the windows up before closing the door your regulator should last much longer. Otherwise Tom (mrbmwx5) had a great fix where he used a piece of house wiring (I used coat hanger :)) to clamp the cable to the bracket where it breaks out. If you do this as preventative it will make the regulator clip more robust and help prevent failure.

replacing oil separator valve to easily reachable location?
 

While so many X5 owners frustrated with oil separator valve problem and especially pain in a neck job to replace it, I was thinking of making some modification to mount it somewhere easy to reach location within the engine compartment. In this caase, we can not use OEM hoses but we may use oil resistant flexible hoses and attach them to the valve and place it at some place within the engine compartment so that one can easily remove and replace whenever it needed.

Anyone please reply how this idea sounds. Has anyone done such a remedy?