How To: Diagnose and Replace a PCV Valve

How To: Diagnose and Replace a PCV Valve

Hey everybody… John here from O’Reilly Auto Parts to talk
to you about some of the signs your vehicle has a bad PCV valve. PCV stands for positive crankcase ventilation. The PCV system removes harmful oil vapors
from the engine and prevents them from being released into the atmosphere. The purpose of the PCV valve is to control
the flow of the vapor from the crankcase to the intake manifold. This valve is typically located in or near
the valve cover. It’s considered a maintenance item, so it’s
important to replace it regularly. Some manufacturers recommend replacement as
often as every thirty thousand miles. If you’re having severe symptoms or aren’t
completely sure about diagnosing this yourself, we’d be happy to recommend a professional
technician in your area… But here are a few of the symptoms you might
be noticing if your PCV valve is failing: The most obvious warning signs are: smoke
coming out of the tailpipe or excessive oil consumption. If the PCV valve is stuck in the open position,
it will draw excess vapors from the crankcase and burn more oil than expected. Another clue is an engine that’s running
roughly due to oil-contaminated spark plugs. This may also be due to excessive flow from
the PCV valve. Even if your car isn’t running roughly,
your oil can provide clues that the PCV valve is failing. Check for oil spots on your garage floor…
a leak could be caused by excess crankcase pressure from a clogged valve. It’s possible this could cause gasket failure. And when you change your oil, keep an eye
out for sludge draining from the tank… it could be caused by a faulty valve allowing
combustion gasses to blend with your oil. 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. We’ll show you how it’s done on this 2005 Jeep Liberty. There will be slight variations from one vehicle to the next, so know the specifics for your vehicle before getting started. First, locate the PCV valve. Ours is here on the passenger side in the oil fill tube. Disconnect the vent hose that goes to the intake. Twist the valve counter clockwise to release it from the oil fill tube. You’ll have to pull on it to release it once the tab is disengaged. Attach your new valve by turning it clockwise onto the oil fill tube and engaging the tab. Reconnect the vent hose to the intake. You’ll find everything you need for this
and other jobs at your local O’Reilly Auto Parts store or Our DIY videos are designed to help answer
questions we get in our stores every day. If you found this one helpful, subscribe to
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About the Author: Michael Flood


  1. To understand: what force cause the PCV spring works (open/close)?… the vacuum or the pressure of the crankcase? …. because I have problem: I saw high vapor come out from the oil cap. wonder why! ….. I replaced with a after marker pcv valve 2 month ago.
    some one told me maybe i have blowby problem. I know what cause too much blowby, but before go throw the piston ring I wonder if with a oil catch can can fix this.
    But my question is, the pcv valve maybe is defective and no working properly to release that pressure??? PLEASE HELP !!!

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