Annoying noise and air sucking in through oil filler cap

Hi and welcome to 2CarPros.

I need you to confirm something for me. Are you sure it is a vacuum and not pressure blowing out of the oil cap? It is really unlikely that you would get a vacuum there. However, if that mileage you listed is correct, it would be very likely that you would have excessive crankcase pressure due to what is called blow-by. That occurs when the piston rings wear and allow compressed air to enter the crankcase and is commonly diagnosed by excessive air pressure coming from the oil cap.

Now, the PCV would be my first thought if it was air pressure blowing out. However, if there is a vacuum, as you mentioned, the PCV would be adding more vacuum because it is designed to draw crankcase air out of the engine via its own vacuum and recirculate it through the combustion chamber.

With that, please reconfirm it is a vacuum and not pressure pushing out that you hear. Also, if you could record what you are hearing and upload it, it may be helpful.

Let me know.
Joe

Thank you for the reply, but I’m sure it’s sucking in. And not just a little, it’s sucking a lot of pressure. And no not blow-by, it’s not blowing out of the valve cover.

Interesting. Where is the oil leak? Honestly, I'm starting to question of the intake is leaking at the base. Let me know where the leak is located. Also, other than the noise, are there any driveability issues?

The leak is located somewhere on passenger side of engine, I didn’t inspect it fully. The car might feel a little slower. Are you saying that the intake gaskets might be bad? And that there’s a vacuum leak?

Welcome back:

If the leak is up higher on the engine, I question if somehow intake vacuum when the engine is running is being drawn into the crankcase. The interesting thing is, the PCV is to eliminate excessive crank case pressure. You have the opposite problem which is odd.