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Q: Strange sound in the engine

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I had my PCV valve replaced. Since then, I can hear a sound in the engine that comes and goes. I tried to diagnose it myself and I discovered a strong vacuum in the dipstick and oil fill oil. When I unplug the hose from the PCV valve, I can feel the PCV valve suctioning air also.

There should be a vacuum coming from the oil fill hole with the engine running. This is because vacuum is created inside the engine as the piston moves downward in the cylinder. Also, you should feel vacuum when holding your finger over the PCV valve with the engine running. This indicates proper vacuum is reaching the valve. To summarize, everything you mentioned indicates the normal system operation. The noise you are hearing is most likely unrelated to the PCV valve replacement. I suggest you have a trained professional inspect your vehicle firsthand in order to diagnose the sound in your engine.

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