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Repla­cing a car’s PCV valve

Not every vehicle has a PCV (pos­it­ive crank­case vent­il­a­tion) valve. If yours has one, and your engine has been idling roughly or a mal­func­tion indic­at­or light goes on, check the PCV valve to make sure that it isn’t clogged with sludge from the con­tam­in­ants in the exhaust fumes or stuck in the wide-open pos­i­tion.

The PCV valve is a vital part of the emis­sions con­trol sys­tem on most vehicles. The PCV valve is usu­ally plugged into a rub­ber grom­met in the valve cov­er, as shown here:

A PCV valve located in the valve cover.

A PCV valve loc­ated in the valve cov­er.

It may be loc­ated on or near the intake man­i­fold, as shown here.

A PVC valve located on the valve cover, with the hose that leads to it removed.

A PVC valve loc­ated on the valve cov­er, with the hose that leads to it removed.

A hose lead­ing to the PCV valve is often kept in place by a clamp. Some­times there’s a little L‑shaped hous­ing on the end of the hose that cov­ers the end of the valve.

Fol­low these instruc­tions to remove your vehicle’s PCV valve in order to check, clean, or replace it with a new one:

  1. Loc­ate the PCV valve and loosen the hose clamp if there is one, or pull the little L‑shaped hous­ing off the end of the valve.

  2. Remove the valve.

    Some PCV valves are held in place with a rub­ber grom­met and can just be pulled free. Oth­ers are threaded into place. If you can’t unscrew the valve by hand, try to grasp its base with the open end of a com­bin­a­tion wrench or a small cres­cent wrench.

  3. Check the hose and the hose clamps or grom­met.

    Remove the hose and blow through it. If the hose is dry, brittle, soft, spongy, or full of sludge or hard depos­its, you should replace it. If the clamps are rusty or the grom­met looks deteri­or­ated, you should replace them, too.

  4. Screw in the new valve.

    If the new valve screws into place, do this by hand to avoid strip­ping the threads in the valve cov­er. Make sure that the valve is seated securely (it should stick just a little when you try to unscrew it again), but don’t over-tight­en it!

  5. Recon­nect the hose to the PCV valve.

    Start the engine, and check around the PCV valve for leaks.

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