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What Is a PCV Valve?

A PCV valve on an engine valve cover.

What is a PCV valve used for in your car? Though it’s not as well known as other car automotive parts, this valve plays a significant role in helping your car function, so there are some excellent reasons to learn more about this unsung hero.

What Is a PCV Valve?Replacing the PCV valve when necessary will protect engine health.

“PCV” is an abbreviation of “positive crankcase ventilation.” This car part is a one-way valve affixed to your vehicle’s crankcase. The crankcase contains your car’s motor oil, and it’s placed at the base of the engine.

As your engine consumes fuel, it generates gases. Most of these gases are managed by your car’s emission control devices, but some wind up in the crankcase. When this happens, the gases mix with the crankcase’s motor oil to produce sludge that can clog your car’s engine. Additionally, these gases may bypass your car’s emission control devices and leave the vehicle via the exhaust system, creating pollution that harms the environment.

The PCV valve was created to manage gases that have made their way to the crankcase. In doing so, the valve protects engine health by preventing sludge from forming and protects the environment by reducing polluting emissions.

How Does a PCV Valve Work?

The PCV valve routes the gases that enter the crankcase back to the combustion chambers of your car’s engine. Once the gases are there, they can be burned without damaging your vehicle or polluting the planet.

The PCV valve is a one-way street. Gases can leave the crankcase via this valve, but they can’t use it to return. This ensures that gases exiting via the PCV valve never reenter the crankcase.

How Long Does a PCV Valve Last?

In some cases, the PCV valve may last the entire life of your car. Some experts say that as long as there are no obvious problems, it never needs to be changed.

However, certain car manufacturers have a different outlook. Some automakers advise that the PCV valve should be replaced somewhere between 20,000 and 50,000 miles of driving. Consult your owner’s manual to find out what your automaker recommends for the care of this valve.

What Are Signs of a Bad PCV Valve?

These signs can indicate that you have a worn or defective PCV valve:

  • An illuminated check engine light
  • Visible oil leaks
  • Visible sludge around the engine
  • Blown-out gaskets or seals
  • Engine whistles while running

You can check the health of a PCV valve by removing it and shaking it. The valve is located in the valve cover, on or near the intake manifold. If you hear a rattling noise, this indicates that the PCV valve is working well — the valve is opening and closing as it should. However, if the valve is silent when you shake it, it may indicate that gas deposits have sealed it shut. A valve that’s sealed shut won’t work properly.

If you think your car’s PCV valve needs to be replaced, you can handle the job yourself or consult a service technician. If your car is experiencing the symptoms discussed above and you’re uncertain about whether a PCV valve is to blame, your best bet is to get the problem diagnosed at an auto repair shop.

The engine is a costly item to repair. Your car’s PCV valve protects the health of this vital component, so it’s important to give it care when it needs it.

Check out all the PCV valve products available on NAPA Online, or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on PCV valves, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Warren Clarke View All

I'm a writer and editor who's a regular contributor with the New York Daily News and Carfax, and my content has appeared in over 20 publications. I've written content that covers industries such as automotive, medical, insurance, healthcare, real estate, plumbing, pest control, dental and hospitality.

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