cyclone valve
 

Im almost positive of this but thought I would ask. Is the cyclone valve the same as the crankcase vent valve and oil separator?

I had yellow mustard looking stuff and condensation on the oil fill cap on my 03 x5 3.0 and was told its my cyclone valve...I'm hoping its not going to be a big deal!

The crankcase ventilation valve has an oil separator on the bottom of it. The separator uses a cyclone action. So, I could see how someone could call it a cyclone valve, maybe even BMW does, not sure.

The oil separator/crankcase ventilation valve is not the cause of the white/yellow pasty stuff under your oil filler cap. That residue is caused by too many short trips, the engine not getting hot enough to burn off the condensation, etc. That same stuff causes problems with the crankcase ventilation valve, when it freezes in the lines. So, someone was confusing cause and effect when they told you the valve caused this, IMO.

Yeah JCL is right, its caused by frequent short trips. Alot of members are having this issue. I had it too. I was told by the dealership it was normal and not to worry about it, but I had the oil changed anyway.

How many miles on your 2003?
 

Dave, you should get that oil separator replaced asap. It is definitely gunked up inside. This should be added to everyone's preventative maintenance at 50k, only if you live in a high humidity climate + freezing temps. This is the recipe for oil separator failure. Mine just exploded, causing 3500 dollars in damage.

Well I got my car back yesterday...$990 to fix it, no warranty. Is this something that will probably happen every winter? When I was at BMW they said that there is 6 other cars in the shop for the same problem.

Dave, was it the oil separator?
 

My valve cover developed a leak, so instead of a $990 bill like you got, mine was much more. Labor on mine was 10 hours.

My guess is these oil separators fail on 4 year old cars and older from years of gunk building up in the separator. Surely BMW would know the exact number of failures (who manufactures these oil separators?)

It could have been worse- the engine could have locked up.

Cracked valve cover and oil seperator, I had the same problem too. But I can tell you right now, there's no way that it takes 10 hours of labor to do..thats blasphemy.. The dealer will rape you..