01 Taurus Duratec DOHC Intake Manifold Noise

Howdy,

I have recently acquired a 2001 Taurus with a 24 valve Duratec 3.0 engine. I noticed that there is a noise almost like a hissing noise coming from the area of the intake manifold. Maybe it is a loose vacuum hose or maybe a loose/bad PCV valve. Any suggestions? It almost sounds like it is coming from underneath and towards the firewall side of the manifold.

Can these plastic manifolds develop a crack or a bad seal that would cause a hissing noise? If the manifold has developed a crack or a bad seal, what impact would I see in the performance? The engine appears to run fine, just a little loud.

thanks, weekendmac

Are you listening for the hiss in your garage? If so, can you still hear it if you park the car in the middle of an empty, quiet parking lot? Maybe you are hearing a reflection off a garage wall or something.

If you can still hear it outdoors, then since the car seems to idle and run fine, and I'm assuming your fuel economy is reasonable still, you may have a bearing that is going bad on the idler pulley, self tensioner, or alternator. What condition is the serpentine belt in? Or possibly you have a slight exhaust leak.

-Rod

Rod -
Thank you for the input. I was listening to it outside with the car running in park. It is really loud (not hard to hear it). I isolated the hiss near the manifold area. I have never heard a noise like this before and was not sure where to start the investigation. In fact, I couldn't even see the PCV valve. I am guessing that it might be below the intake manifold. I am not certain what other vacuum lines are behind/below the manifold that I can not easily see. It would seem like the vacumm lines would be the easiest place to start eliminating posibilities.

In preparing this post, I was guessing that there might be some history with the plastic intake manifold (only because it was plastic and plastic does not last forever like a casted part would). I have not had a plastic one before and I not sure what to expect.

First, is this hissing noise common/normal for this car/engine? If not, where would you start?

Thanks!!

Well, if you are not experiencing idle issues or stumbling under load, I'd be a bit surprised if you have a sizeable enough vacuum leak to be as audible as you describe.

Without actually experiencing the sound though, it's hard to state if the sound is normal. The Taurus is a pretty common car, maybe you can find a co-worker with a similar model Taurus with the same engine and see if they'd let you take a listen under their hood.

-Rod