The CrankCase Ventilation valve is also known as CCV valve, PCV valve, or the oil separator. The CCV valve is found under the hood of your vehicle, and it is a fuel vapor recycler. The primary function of the crankcase ventilation valve is to recycle blow-by gases back to the crankcase to be reused, thereby preventing damage to your BMW’s engine.
Blow-by gases are vapors of unburned fuel released by the engine, which is heavily toxic. If these vapors are left inside the crankcase, it eats away at components inside your vehicle. This was why the CCV valve was designed to ventilate these vapors. The CCV valve sucks away the partially-burned gases from the crankcase through the intake manifold and returns them to the engine to be properly burned.
However, in a situation when the valve fails, the toxic blow-by would not be extracted from the crankcase, which in turn wreaks havoc inside your BMW’s engine.
Causes of Crankcase Ventilation Valve Failure
Although the CCV valve rarely fails, the valve filter is mostly the root cause of a failure. The valve filter, just like other filters in your vehicle, is responsible for filtering unwanted particles. In this case, the function of the filter is to capture most of the toxins in the blow-by gases.
However, natural wear and tear will occur after a long period of use, and the filter can become clogged with road debris and dirt. The overheating of your BMW engine may also cause the seal of the CCV valve to crack or break, thereby preventing it from closing completely whenever the need arises.
While the regular service of the crankcase ventilation will help ensure its longevity, it is recommended that the valve filter be replaced every 60,000 miles. On the other hand, the crankcase ventilation valve does not have a definite time for replacement and would only need to be replaced when it becomes defective.
Symptoms of a Defective Crankcase Ventilation Valve
When the ventilation valve becomes stuck in the open or closed position, or there is a disconnection of the system hose, the CCV fails. When it fails, you may notice the following symptoms:
- Illumination of Check Engine Light: A failure of the CCV valve may cause a too lean or too rich fuel/air mixture. When the powertrain control module detects this, it notifies the driver by turning on the check engine light on the dashboard. While a failed CCV valve might have caused your check engine light to illuminate, you should visit your mechanic for a complete engine inspection because the failure of other parts can cause the check engine light to come on.
- Difficulty Starting or Rough Idle: When your valve gets stuck in the open position, the CCV valve will no longer be able to control airflow. This causes the engine to receive an air/fuel mixture that is too lean because of more air than necessary in the mix. Consequently, your vehicle might experience a rough start or idle roughly.
- Increased Oil Consumption and Oil Leaks: An increased pressure in the crankcase may cause your CCV to fail, thereby causing oil leaks through the seals and gaskets. You may notice oil sludge on the ground of your garage where your BMW is parked. The leaks will also result in increased oil consumption.
- Other symptoms you may notice include increased engine pressure, failure of the seal/gasket, emission of black smoke, oil in the MAF sensor, etc.
You should not attempt to fix the issue yourself because, apart from the possible likelihood of causing costly damage in the repair process, there is a high chance the symptoms resulted from a faulty MAF sensor. So it’s best to have this diagnosed with proper equipment before proceeding with any repairs.
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