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Tips to Maintain the Crankcase Ventilation Valve in Your BMW

When most of us think about the essential parts of a car, we think of four wheels and a seatbelt, doors and windows that operate correctly, working lights, and an engine to run it all. From there, we remember the parts we see and the parts that break down and send us to the mechanic. One of the parts we do not often see or think about is the PCV (or Positive Crankcase Ventilation) Valve.


What is the purpose of the PCV Valve?

Not much bigger than your thumbnail, this small piece plays an important role in the running of your vehicle. It regulates the flow of combustible gasses (as opposed to fuel) back into the combustion chamber. To understand the role of the PCV Valve, you need to understand that your BMW runs by the power of small, controlled explosions in your engine, which force the transmission to turn your wheels and propel you forward. In any kind of explosion, there are gasses that escape, pushed out by the explosive force.

Think about boiling water in a pot. If you turned up the heat to 600 degrees, the water would boil very fast, almost explosively fast, and it would probably boil over the edge of the pot it contained. It would not simply turn to seam and float up in the air peacefully. If you were standing nearby, you would get hit with very hot, still very liquid water.

The fuel that burns in the engine burns and creates gasses that do not all automatically burn. Some gasses escape out, just like the scalding water, and if they are allowed to just float around inside your car, they can cause damage, and at the very least, create air pollution around your car and perhaps in your air vents.

This is where the PCV Valve comes in. It redirects those gasses right back into the combustion chamber, which not only prevents them from poisoning the air or damaging other parts of the engine, it gives you an extra push in your combustion which improves your gas mileage. Whether you care more about the environment or paying less at the pump, the PCV Valve is your best friend.

How can you ensure your PCV Valve is functioning properly?

In BMWs the most common problem with PCV Valves is getting plugged with oil and fuel residue. When this happens, you begin to lose gas mileage. To test your PCV Valve, follow these steps:

  1. Remove your PCV Valve and give it a shake. If you hear a rattling noise inside it (the pintle), then you should have good airflow – your PCV Valve is in good shape.
  2. Hold your finger over the valve while the engine is idling. If you do not feel a vacuum than there is a clog in either the PCV Valve (see step 1) or in the hose, which would need to be replaced.
  3. Use a flow tester to check the PCV Valve performance. This is the most definitive way to check the health of your PCV Valve.

If your PCV Valve is not the problem in your BMW, it may be something in the overall system causing you airflow problems. To check your airflow, you need to start your car and get it to operating temperature. While it is still idling, pinch off the vacuum hose to the PCV Valve. The engine RPM should drop between 50 and 80 RPM before it corrects itself. If the motor speed does not change, it means it is used to operating with little to no airflow – which is not good. If the change in speed is greater than 80 RPM, then you have too much airflow. This may indicate that you have the wrong valve for your motor.

BMW Crankcase Ventilation Valve Inspection

If you have any questions about maintaining your PCV Valve or airflow in your engine, contact Ultimate Bimmer Service. They offer quality service on Bimmers and will thoroughly check your car to be sure it is running safely and efficiently so you can drive with confidence down the road to success. Don’t wait until your check engine light goes off and you are stranded on the side of the road. If you think you may be losing gas mileage, bring you BMW in for a PCV Valve checkup today.

* BMW X1 image credit goes to: bruev.

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