The positive crankcase ventilation (PCV) helps create the division of emission-control devices; it routes the leftover combustion gases from the bottom of the engine and the oil pan back into the crankcase where instead of escaping into the atmosphere they are burned in the combustion chambers.

While there are a few newer models of vehicles that don’t have the valve to limit the flow of gases, the majority of vehicles on the road today do have this part. The PCV valve serves to keep the system from clogging by opening and closing on schedule. If the part fails it may result in sluggish acceleration, a rough idle, or increased oil consumption.

A few things to know about your PCV valve

  • Normally mounted on a grommet or valve cover or at the end of the tube, a PCV is pretty easy to evaluate for effectiveness. Remove the valve and shake it, if there is a solid rattling noise then the part is most likely in good working order.

  • Hoses and tubes with gases and exhaust running through them always run the risk of becoming clogged from built-up sludge or excessive leakage. Cleaning the full system whenever you replace the vehicle’s air filter also reminds you to test the airflow through the PCV valve to ensure proper functioning.

  • Oil consumption is increased when pressure builds inside the crankcase. The vapors that aren’t allowed to leave the chamber cause a domino effect; oil won’t flow past gaskets and seals, leading to increased pressure. Alternatively, too much air in the system lightens the fuel-air mixture which will probably result in the Check Engine Light turning on.

  • Flow testers are also a great tool to verify correct functioning of the part as they can check both the air flow and the vacuum at the same time.

Keeping your PCV valve and hose system in good working order assures that the vehicle is receiving the correct ratio of air to fuel and also keeps emissions output under control.

YourMechanic supplies top-quality PCV valves to our certified mobile technicians. We can also install a PCV valve that you've purchased. Click here to get a quote and more information on PCV valve replacement positive crankcase ventilation.

This article originally appeared on YourMechanic.com as How to Buy a Good Quality Positive Crankcase Ventilation (PCV) Valve and was authored by Valerie Johnston.


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