Crankcase Ventilation System Failure in Your BMW

BMWs are unlike any other vehicle on the road, which is why it’s reasonable to imagine that they often encounter specific issues that are unique to the brand. Certain BMW models experience crankcase ventilation system failure, which is a serious problem for drivers; they often encounter oil leaks and other concerning symptoms. If you’re unsure of what the crankcase ventilation system does, don’t panic – in this article we’ll go over the importance of the system and what you can do to prevent failure.

What is the positive crankcase ventilation system?

The positive crankcase ventilation (PCV) system is partially responsible for controlling the emissions released by your BMW into the earth’s atmosphere. It works by recycling the harmful gases that are emitted during the combustion process, also referred to as “blow-by.” It is very important for your BMW’s engine function to have blow-by gases removed from the engine so they do not return to the crankcase; in order to achieve this, the PCV system includes a PCV valve which closes after the gasses are emitted so they do not flow back into the engine and contaminate the quality of oxygen for combustion and ignition processes.

As you can see, it is critical to maintain the various components of the PCV system, otherwise engine function becomes diminished, and the failure of the PCV system can lead to serious performance problems and engine damage.

The most common sources of failure

As we mentioned before, the PCV system contains the PCV valve, which closes off the intake manifold, protecting the combustion chamber from blow-by gasses re-entering. The PCV valve is a part that commonly encounters failure, and often causes serious problems for BMW drivers. If the PCV valve fails, blow-by gases re-enter the combustion chamber and causes several different issues, including an improper fuel-to-oxygen ratio, moisture and sludge buildup, and premature corrosion of engine parts over time. Usually when the PCV valve fails, it’s because a seal or O-ring couldn’t hold up to internal engine temperatures, which could be an inherent design deficit.

Warning signs of a failing PCV system

The warning signs and symptoms your BMW displays are critical to become vigilant of; they can be useful for not only getting you to your automotive shop, but for your automotive specialist to help accurately diagnose the problem. Paying close attention to warning signs of PCV system failure is especially important because if not taken care of quickly, the issue can cause significant engine damage. Here are the most common warning signs of PCV system failure that you should be aware of in your own BMW:

  • Oil leaks
  • Unusual oil consumption
  • Check-engine light illumination
  • Crankcase ventilation filter is dirty
  • Engine stalling
  • Unusual engine noises

If you notice any of the above-mentioned symptoms of PCV system failure in your BMW, it is critical that you bring it to a trusted BMW specialist for evaluation right away – the longer the problem persists, the more likely you’ll run into a significant repair bill down the line.

How to prevent and address crankcase ventilation system failure

Many drivers forego their car’s designated maintenance schedule because they either don’t believe that the tasks are necessary, they don’t have the funds to stay on top of maintenance, or they simply don’t wish to prioritize auto maintenance. However, it’s important to keep in mind that the more maintenance tasks are overlooked, the higher the chances are that you’ll eventually be without a reliable vehicle, will encounter expensive repairs frequently, and will be forced to pay out of pocket at some point. Here are a few helpful tips on how to best give your BMW the care it requires in order for you to enjoy your car more, rely on it more consistently, and save money on repairs in the future:

  • Find an automotive service you trust and that specializes in BMW vehicles
  • Adhere to your manufacturer-recommended maintenance schedule
  • Consult with your automotive expert right away on any concerning symptoms you notice in your BMW’s performance
  • Make sure your BMW specialist utilizes high quality replacement parts


Here at Automotive Imports, BMW clients from all over Boulder, Lakewood, Centennial, Westminster, Littleton, and Denver, CO, have entrusted us with caring for their vehicles for years. We value our clients’ trust, which is why we make it a point to take a preventive approach to every vehicle we service. To learn more about our shop or to get started on your BMW’s maintenance, please call us directly.

* BMW M4 image credit goes to: Chiradech.