Buying the Right PCV Valve

Jefferson Bryant

November 16, 2025

4 min read

Jefferson Bryant

November 16, 2025

4 min read

A mechanic wearing a black nitrile glove holds a PCV valve between his index finger and thumb after removing it from the engine. — Most modern engines use a thread-in PCV valve, not the older push-fit style.

Your engine’s positive crankcase ventilation (PCV) valve protects the oil from becoming acidic and helps reduce emissions. For most modern vehicles, the first warning sign of a failing component is the check engine light. Don’t ignore that warning.

PCV valves are simple devices. There’s a check ball or needle and a spring inside the valve, which opens and closes under set conditions. PCV valves fail in two ways: They either get stuck open or closed.

PCV stuck open: When the valve sticks in the open position, the engine runs poorly and misfires. Other issues include hard starting, black exhaust smoke, and oil-fouled spark plugs.

PCV stuck closed: If the valve sticks closed, the problems are worse, especially when it’s not fixed over time. Fuel economy decreases, and you may hear a whistle or hiss coming from the engine. If left unchecked, the engine develops oil leaks around the oil pan and crank seals.

Modern direct-injection engines need the PCV valve to function. These engines do not get fuel in the intake runners of the cylinder heads, meaning the fuel does not clean the intake valves. The PCV system must be working well to keep oil vapors out of the intake. Otherwise, these vapors cook onto the intake valves and make them sticky, reducing performance.

Two valves covered in carbon build-up, displayed on a metal work surface. — These valves are from a gasoline direct injection (GDI) engine with just 50,000 miles on it. The intake valve (right) has a large mass of carbon build-up on the valve stem, which is caused by too much oil vapor getting past the PCV valve.

How can you test a PCV valve?

Take out the valve and give it a shake. If it rattles, it is likely good. If it does not, it is bad or clogged. You can clean a PCV valve by soaking it in carburetor cleaner for a few minutes and then shaking it again. If the check ball starts rattling without any thud sounds, it can be put back into place.

PCV Valve Vacuum Rating

A mechanic grasps the rubber hose connected to the PCV valve on a vintage engine with a green valve cover. — A push-in PCV valve, of course, pushes into a rubber grommet on the valve cover.

Buy the PCV valve that matches what’s currently in your engine. There are no high-performance PCV valves, even though there are specific PCV valves for sports car engines.

For carbureted engines, the vacuum rating for the PCV valve varies by the engine’s performance level. For example, a 1970 Chevrolet Chevelle with a base two-barrel 350 cubic-inch engine needs a PCV with a higher vacuum rating because the engine generates more vacuum through the intake.

The same car with the high-performance 454 big-block engine uses a PCV valve rated for lower vacuum levels, as the engine produces less vacuum through the intake. This matters because, on carbureted engines, the PCV valve functions as a planned vacuum leak. If you put the low-performance PCV valve on the larger, low-vacuum engine, you end up with a bigger vacuum leak than the engine expects, and it does not run as well at idle.

For modern engines, the intake system is a closed loop, so this is not a factor. In nearly every case, you need to use the original PCV valve design for your engine.

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How much does a PCV valve cost?

Most PCV valves cost between $10 and $50. Some have a more expensive mounting design. You can get away with an inexpensive PCV valve. The advantage of a pricier PCV valve is lifespan. A less expensive valve is likely to fail faster than a name-brand valve.

What to Replace With a PCV Valve

A mechanic points out the PCV valve on a modern engine’s air intake tube. — The PCV valve on modern engines connects to the air intake tube. Inspect the hose for damage.

On older engines, the hose connecting the PCV valve to the carburetor or air tube is soft rubber. It breaks down over time. If your engine has a soft PCV hose, inspect it for cracks, splits, weak spots, or other damage. If it has those issues, replace it. Also, if your engine has a valve mount with a rubber grommet, swap in a new one.

Most modern engines use hard plastic lines for the PCV valve. These do not see the same wear and tear as soft rubber. Inspect hard lines for cracks or damage and replace them as necessary. Modern valves are typically thread-in style, so apply non-hardening thread sealant.

About the author

Jefferson Bryant

A lifelong gearhead, Jefferson Bryant got his first car when he was two: a Fisher-Price convertible. An industry veteran for over 30 years, Jefferson started in car audio, working his way up to product designer for Rockford Fosgate. He has written nine books and countless magazine articles about automotive technology. Jefferson also produces tech videos on YouTube. His pride and joy is a 1971 Buick GS Convertible with a swapped Procharged Gen V LT1, which he used to drive his newborn kids home from the hospital.

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This article is meant to provide general guidance only. Automotive maintenance, repair, upgrade, and installation may depend on vehicle-specifics such as make and model. Always consult your owner's manual, repair guide for specific information for your particular vehicle and consider a licensed auto-care professional's help as well, particularly for advance repairs.