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Eric, Automotive Repair Shop Manager
Category: Ford
Satisfied Customers: 31935
Experience:  Automotive Repair Shop Manager, Technician
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Ford Focus SE: High pitched hissing, whistle, or sucking sound

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High pitched hissing, whistle, or sucking sound coming from under car. I don't know if it's from the front area (engine) or exhaust under the car. I feel it's more pronounced on the driver's side where exhaust runs than the passenger side.
I can't trully say the car doesn't do it when cold, but it's more noticeable when warmed up. While cruising almost at any speed at 1100 to 1600 rpms. It's a very faint sound, not very loud. Can be heard mostly when driving through parking lots or close to buildings and the sound bounces back. I guess it kind of sounds like that whistle that diesel trucks make... but again, not loud at all.
I don't know if it's normal, becuase my wife drives the car all the time and I hadn't really noticed it before.
While at idle, the car has this whistle or high pitched resonance coming from exhaust that has always been there. Don't know if it's related. And it only does it while in D and R, not in N or P. And the pitch does change a little with the rpms. I can hear it go up and down with the revs.

I know it's hard to say without listening and I'm not looking for a diagnosis. I guess just an educated guess or if these characteristics sound like something you guys have seen in a service department. If it's normal, I'll let it go, but if not, I'd rather tackle it now.

Thank you for your time, and sorry about long description.

do you notice either an erratic idle, going up and down while in park or in D but stopped, or a higher than normal idle?
Customer: replied 5 years ago.
No idle issues. Starts up fine, rpms gradually go down as it warms up. Takes off fine, idles perfect, gas mileage and performace are great.

Ok, that eliminated air intake,intake manifold, idle air control valve, throttle body, vacuum hoses and pcv valve.

the most likely culprit is the exhaust, specifically either the resonator or the double wall exhaust pipe leaking.


here is diagram showing them:

Customer: replied 5 years ago.

Great! thanks for your info... at least I have an idea of what to possibly suggest to the shop. On a side note, I don't know if it can be related, but I do have a vibration/rattle/buzzing sound coming from the area under the shifter area. Possibly a loose heat shield according to another tech here. So could these be related?


Thanks again, I'll most likely visit an exhaust shop for this instead of going through the dealer.


yes, this is usually the heat shield where the tac welds break. they can rewelded in about 10 minutes to resolve that issue. If the heat shield is hitting the exhaust pipe it could be resonating thru it and creating the other noise.

I would definitely have this done by an exhaust shop to save yourself the high dealership rates
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