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What Does a PCV Valve Do

March 10, 2016 | Engine Info

What Does a PCV Valve Do

The PCV, an abbreviation for Positive Crankcase Ventilation, is a control device whose purpose is to send partially burned gases to the engine’s combustion chamber from the crankcase of the engine. The PCV is one of the oldest and most used emission control devices. Its name may make it sound like a very complicated device but in truth, the PCV is a fairly simple device whose functions can be understood easily.

What Does a PCV Valve Do?

One of the main tasks of the PCV system is to remove a major contaminant from the oil. This contaminant is water. Because of the tasks performed by the PCV, the PCV valve has various other benefits besides its usual usefulness. The PCV valve completely eliminates the emissions from the crank case with great efficiency so that it doesn’t contribute to the air pollution and also keeps the entire system moisture free with the implication of constantly circulated air. It also extends the engine’s life by keeping the oil and engine in proper shape.  The mechanism of the PCV is very important in preventing the corrosion of the engine and improving the fuel economy by doing so. Looking at it like this, the PCV is a very important component of a car which not only extends the life of the engine but also improves the fuel economy.

The PCV valves routes the partially burned gases emitted from the crankcase back to the engine and which upon, their return to the engine, are burned again and save the fuel in doing so. The combustion cylinders play an important role in this process since the gases are burned in those cylinders. The PCV plays an important in maintaining a clean air environment as well since the partially burned gasses are a factor which greatly contributes to the air pollution. Not only this, the PCV also requires little to no maintenance and must only be replaced after the car has traveled about 40 miles or so.

Symptoms of a Bad PCV valve

The symptoms of a bad PCV valve can vary depending on its way of failure. For example, a PCV valve that sticks open may light up the check engine light and the DTC doesn’t mention the PCV normally except for DTC P0171 and P0174 which may suggest a lean condition in the engine while some other engines could set an oxygen sensor code or a mass-air-flow meter code.

Another symptom of a faulty PCV is emission of noise. This noise may a whistle, whine or a low moaning noise. In case of the noise, the best method to trace it is to block the vacuum source to PCV valve to see if noise changes or disappears. Another symptom is the oily or dirty spot near the PCV inlet hose since a faulty PCV valve can make the oil to blow onto the air filter element.

A failed PCV system can cause oil leaks and severe buildups of sludge.

Read also: What Does White Smoke From The Car Exhaust Mean

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