The PCV valve is one of the smallest and cheapest parts on an engine, yet a stuck one causes symptoms that look far more expensive, from oil leaks to a rough idle.
What it does
As an engine runs, some gases slip past the pistons into the crankcase. The positive crankcase ventilation, or PCV, valve routes these gases back into the intake to be burned, instead of letting pressure build up or venting to the air.
Signs of a bad PCV valve
- Oil leaks from seals and gaskets due to pressure building up inside.
- A rough or high idle from a vacuum leak through a stuck valve.
- Increased oil consumption or oil in the intake.
- A check engine light in some cases.
Why it is worth checking
Because it is cheap and easy to replace, the PCV valve is worth ruling out before chasing expensive leak repairs. Many oil leaks and rough idles trace back to this little valve.
Frequently asked questions
How often should a PCV valve be replaced?
Many last a long time, but checking it every 30,000 to 50,000 miles and replacing if stuck is good practice.
Can a bad PCV valve cause oil leaks?
Yes. If it clogs, crankcase pressure rises and pushes oil past seals, which then leak.
See our car accessory guides for maintenance parts.
