Symptoms
- Rough or unstable idle
- Whistling noise from the engine bay
- Increased oil consumption or new oil leaks
- Never heard of or checked the PCV valve before
Likely causes
- CommonValve stuck closed from carbon buildupThis can cause pressure buildup in the crankcase, leading to oil leaks from seals and gaskets.
- PossibleValve stuck openThis can cause a vacuum leak, leading to a rough or high idle.
- CommonValve simply never replaced despite ageIt's a low-cost part that's easy to forget since it doesn't have a dashboard reminder.
What to do
- Locate the PCV valve, usually a small valve inserted into the valve cover with a hose attached (check your manual for exact location).
- With the engine running, pull the valve out slightly (leaving the hose attached, if possible) and check if it rattles when shaken; a healthy one should rattle.
- Look for oil residue or a clogged look inside the valve or the hose leading to it.
- If it doesn't rattle, looks gummed up, or is original after many years, replace it since it's a cheap and easy part.
- Clear any related hoses of sludge buildup if you find residue while you're in there.
- After replacement, confirm idle smooths out and check for any oil leaks that were present before.
Tools and parts
- Basic hand tools
PCV valve for your engineSearch: “PCV valve for [your car year make model]”
When to call a pro
If idle problems or leaks continue after replacing the PCV valve, have a mechanic check for other vacuum leaks or gasket issues.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.