How to Diagnose and Replace a Bad PCV Valve

The PCV (positive crankcase ventilation) system in your vehicle removes harmful oil vapors from the engine and prevents them from being released into the atmosphere. The PCV valve is designed to control the flow of the vapor from the crankcase to the intake manifold. This allows the vapors to be burned in the engine and prevents them from polluting the atmosphere, while also ensuring that internal engine pressures do not reach dangerous levels. Excess internal pressure in the engine due to oil vapor buildup can cause gasket damage and leaks, and may also hinder performance and efficiency. PCV valve replacement is considered a routine automotive maintenance task, so it’s important to replace the valve at the first sign of a problem. Some manufacturers recommend PCV valve replacement as often as every thirty thousand miles. For more information about the recommended replacement interval for your car, truck, or SUV, take a look at your vehicle’s owners manual.

  1. Tools & Materials List
  2. Step by Step Instructions
  3. Additional Resources

Tools & Materials

Safety Eye Glasses Safety Glasses

Protective Gloves Gloves

PCV Valve PCV Valve

Diagnosing PCV Valve Symptoms

Before replacing your PCV valve, you should check for some of the most common signs or symptoms of a bad PCV valve.

Smoke or Excessive Oil Consumption

One of the most obvious warning signs your PCV valve may need to be replaced is black or gray smoke coming out of the tailpipe or excessive oil consumption. If the PCV valve is stuck in the open position, it will draw excess oil vapors from the crankcase and burn more oil than expected.

Rough Engine Idle

Another clue that points to a faulty PCV valve is an engine that’s running rough due to oil-contaminated spark plugs. This may also be due to excessive flow from the PCV valve, damaged piston rings, and other factors.

Other Symptoms of a Bad PCV Valve

Even if your car isn’t running noticeably rough, your oil condition and leaks can provide clues that the PCV valve is failing. Check for oil spots on your garage floor. Excess crankcase pressure from a clogged valve can cause gasket failure. And when you change your oil, keep an eye out for sludge draining from the pan; it could be caused by a faulty valve allowing combustion gasses to blend with your oil.

Do It Right: Keep an eye out for any or all of these symptoms. If you have a faulty PCV valve, it’s important to replace it before any other damage occurs. For most vehicles, this is a project you can do yourself.


Step-By-Step Instructions to Diagnose and Replace a Bad PCV Valve

With the right tools and parts from O’Reilly Auto Parts, replacing a bad PCV in your vehicle is a repair you can do yourself. Follow these step-by-step instructions to replace your PCV valve right the first time. Be sure to check your vehicle’s owners manual or service manual for repair steps specific to your vehicle. If you’re experiencing severe symptoms or aren’t completely sure about diagnosing this yourself, we’d be happy to recommend a professional technician in your area.


locate the pcv valve. shown here next to the oil fill tube

Step 1: Locate and Remove the Old PCV Valve

First, locate the PCV valve. In our example, the valve is located on the passenger side oil fill tube.

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disconnecting the hose

Step 2: Disconnect the Vent Hose

Now disconnect the vent hose that goes to the intake.

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twist counterclockwise and pull once the tab undone

Step 3: Detach the Valve from the Oil Fill Tube

Next, twist the valve counterclockwise to release it from the oil fill tube. You’ll have to pull on the valve to release it once the locking tab is disengaged.

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attach by turning clockwise and engage the tab

Step 4: Install the New PCV Valve

Now you can attach your new PCV valve by turning it clockwise onto the oil fill tube and engaging the tab.
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reconnect the hose

Step 5: Reconnect the Vent Hose

Finally, reconnect the vent hose to the intake.
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Additional Resources

How to Change Your Oil in your vehicle

How to Change Your Oil and Filter
Change fuel filter in car

How to Change a Fuel Filter
checking fluid levels

How to Check and Fill Fluids

The automotive repair work depicted in this series is performed under the direction of the manufacturer of the product featured. Prior to undertaking any of the demonstrated repairs on your vehicle, we suggest you consult with a certified mechanic or another professional who can adequately advise you of the proper repair or remedy required. O’Reilly Automotive Stores, Inc. and its affiliates (“O’Reilly”) disclaims any responsibility for injury or damage resulting from a viewer’s attempt to recreate the repairs shown in this series.