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Replacing Your PCV Valve Diaphragm

What is a PCV Valve Diaphragm?

A PCV valve diaphragm is a large rubber component of positive crankcase ventilation or PCV valve. This system uses an inlet hose to supply clean air to the engine. The PCV valve diaphragm also separates an inlet filter that cleans its incoming air. The PCV valve diaphragm relieves pressure and directs fumes from the crankcase to the engine by creating a slight vacuum—these fumes burn and regulate the amount of airflow.

If the PCV valve diaphragm is damaged in any way it can lead to oil leaks, sludge buildup, and other issues.

Signs of PCV Value Diaphragm Failure

When the PCV valve starts to fail, it can show in a few ways. It can manifest in fault codes about cylinder misfires, your check engine light may be on, or there could be a strange intake noise. You may also notice idling or stalling, oil leaks, sludge, excessive emissions, and fuel consumption, or poor acceleration. When these signs become evident, replace your PCV valve diaphragm as soon as possible. A new PCV value diaphragm will help your car to run more smoothly and efficiently.  

What the PCV Valve Does

The PCV valve is located in the engine valve cover and connected to the intake manifold or throttle body through a vacuum hose. The PCV valve’s function is to reduce pollution and regulate blowby by redirecting gases from the crankcase back into the engine to be burned.

During acceleration, gas flows through the PCV valve into the engine. Without the PCV valve functioning properly, oil can be left in the air filter or gas can be redirected into the environment.  

The Advantages of Replacing Only the PCV Diaphragm

Replacing only the PCV diaphragm instead of the entire PCV assembly has many benefits. You can save significant amounts of money, ensure higher quality material that will help to maximize lifespan, and helps to retain high-quality OEM PCV assembly and oil separator. After removing the PCV assembly has been removed, the installation of the PCV diaphragm is very quick and easy.

In some cases, you may need to replace the complete valve cover assembly, but more often you just need to replace part of it—which can save you significant amounts of money. In most cases just purchasing the PCV valve is a much more practical purchase than the entire assembly. Both Volkswagen and Audi do not sell this as a spare part, which would require you to buy the entire assembly, or you could come to RKX Tech where we have diaphragms made of high-quality Viton for Audi and Volkswagen.  


At RKX Tech, we carry PCV valve diaphragms for several applications. These include Audi 4.2L & 5.2L FSI 2004-2011 and Volkswagen 4.2L FSI 2006-2011.

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