Oil Separator Info / True solution.

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This is very long but it will save you a lot of grief and big $$$. Many of us have seen it. Heavy smoke coming out the tail pipes, then so much smoke you think you’re on fire. I bought my X5 2001 4.4, that way because the previous owner thought they blew the engine and the dealer repair price was outrageous. I followed info from this forum and changed all the recommended parts, did it with a friend, $600 later I was fine.

Next winter (last month) it happened again. I opened the hood and saw oil all over the right side of the engine from top to bottom like and explosion. It was cold, single digits and happened after 15 minutes of driving. I was able to leave the car in a safe place and went to work. At noon I went back, it has warmed up and the heat of the engine helped. I checked the oil, it was down about two qts so I started it. Oil did not leak from the engine so I drove it home. Smoke continued to come out but less and less as I drove.

Degreased the engine at home and topped off the oil. Drove again with the dipstick slightly pulled out (I’ll explain later). At first my plan was to locate where the oil came out so I could replace that part only since we already did this job. Not a drop came from anywhere, then I drove to work, still full of oil as if nothing happened.

I looked at it real closely with a friend (BMW expert), all parts were functioning perfectly. We then ran several tests to determine root cause, here it is:

Most of this is known but I’ll go through it step by step

· Oil separator valve is needed to recirculate crankcase pressure back to the intake manifold and through the combustion chamber.
· Short trips do create moister in the oil and it can easily collect in the oil separator
· Single digit temps will cause the oil separator to freeze and stop the airflow to the intake manifold, crankcase begins to pressurize.
· Pressure builds in the crankcase and actually forces its way up into the combustion chamber, oil starts burning and tons of smoke will come out the back.
· Eventually the pressure will burst the weakest point.

In my case it came out of the oil filler cap. Oil was all over the washer fluid container, nothing on the 4.4 x5 engine is high enough to send oil where it did. Except the oil filler cap, the pressure was great enough to blow it right by the seal. Remember after I cleaned it, not a drop of oil came out from anywhere. Because the parts were new, valve cover gasket, oil separator and lines, they were able to withstand the pressure. The cap ended up being the weak point.

When you take it in at this point the dealer automatically changes all the parts associated with this failure. 9 times out of 10 it’s not needed. We actually created it again by blocking the oil separator and letting the pressure build up again. This time I had the cap on slightly loose so I wouldn’t do any damage and sure enough when the pressure reached a certain point it blasted out of the cap like a fire hose (sideways and down).

In the end I didn’t replace anything, I gave it an oil change and have been running for 4 weeks fine, it drives like new, I’m at 90K miles and it happened the first time at 84K. Although this could happen every time it gets cold, but when it thaws out the system may be just fine unless something burst.

The other thing we discovered and maybe most import is the dipstick seal. It’s a double Oring that will hold a fairly high pressure, sometimes it’s hard to pull it out by hand. If it gets real cold just pull it out and put it back with only one o ring in the tube, just don’t fully seat it. You will be able to see the top Oring sticking out of the dipstick tube. Make sure there isn’t any resistance when you pull it out, do it a few times. You now have created a pressure relief valve. If this happens again it will shoot your dipstick out and dump a bit of oil in that area. Not the best solution but mine is in this position because I don’t plan to do this job again.

Bottom line it’s a real crappy design but I feel a little better about it now that I know exactly whats going on. I may actually buy a smaller size oring for the dipstick so it’s sure to come out if the oil separator freezes.