yellowish "Goo" on oil filler cap?

[JCL]

It is not the crankcase vent valve, also known as the oil separator. It is due to condensation in the engine, which emulsifies with the oil. It is the result of doing lots of short trips where the engine doesn't get hot enough. If the engine does get hot enough, the condensation boils off. If it doesn't, it collects over time, often under the oil filler cap.

Now here is the connection to the CCV, or OSV: the condensate can collect in the crankcase vent valve, and clog it up. If it gets cold enough, the condensate can freeze, blocking the valve. That is when you get problems. The CCV is not the cause, it is where the symptoms can occur. Since it is so often mentioned in conjunction with this problem, people assume that the CCV is the cause.

The cure is to do a few hot oil changes in short order, and ensure that your driving includes a few longer trips that keep it at bay. You may want to get the CCV checked and cleaned out if you live in an area where it gets significantly below freezing, to manage the risk of a failure there. If you don't live in a very cold area, there is limited risk.

[msammy]

JCL is right! I also get this "cheese whiz" every winter but luckily, I garage my X5 so it never gets a chance to freeze up in the oil separator and has never been a problem. Once spring and summer arrives, the condensate burns off and the "whiz" is completely gone. Since we're nearly half-way out of Winter and the sub-freezing temperatures have subsided in most parts of the country, don't spend the money replacing the oil separator - try doing an early oil change instead to clear some of the condensate out so that it doesn't freeze if we get another big chill before winter is over!

[FSETH]

Originally Posted by JCL

It is not the crankcase vent valve, also known as the oil separator. It is due to condensation in the engine, which emulsifies with the oil. It is the result of doing lots of short trips where the engine doesn't get hot enough. If the engine does get hot enough, the condensation boils off. If it doesn't, it collects over time, often under the oil filler cap.

Now here is the connection to the CCV, or OSV: the condensate can collect in the crankcase vent valve, and clog it up. If it gets cold enough, the condensate can freeze, blocking the valve. That is when you get problems. The CCV is not the cause, it is where the symptoms can occur. Since it is so often mentioned in conjunction with this problem, people assume that the CCV is the cause.

The cure is to do a few hot oil changes in short order, and ensure that your driving includes a few longer trips that keep it at bay. You may want to get the CCV checked and cleaned out if you live in an area where it gets significantly below freezing, to manage the risk of a failure there. If you don't live in a very cold area, there is limited risk.

I agree as well. I just see these "goo" on oil filler cap threads and push the O.P. to search oil seperator issues so they can see what the "goo" means. I would do as JCL suggested. Good advice.

[JS_4.8]

Originally Posted by JCL

It is not the crankcase vent valve, also known as the oil separator. It is due to condensation in the engine, which emulsifies with the oil. It is the result of doing lots of short trips where the engine doesn't get hot enough. If the engine does get hot enough, the condensation boils off. If it doesn't, it collects over time, often under the oil filler cap.

Now here is the connection to the CCV, or OSV: the condensate can collect in the crankcase vent valve, and clog it up. If it gets cold enough, the condensate can freeze, blocking the valve. That is when you get problems. The CCV is not the cause, it is where the symptoms can occur. Since it is so often mentioned in conjunction with this problem, people assume that the CCV is the cause.

The cure is to do a few hot oil changes in short order, and ensure that your driving includes a few longer trips that keep it at bay. You may want to get the CCV checked and cleaned out if you live in an area where it gets significantly below freezing, to manage the risk of a failure there. If you don't live in a very cold area, there is limited risk.

I just want to say this is an excellent description of the symptoms and possible consequences of this ever so common problem. Great job!