Occasional hooting sound.

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99WhiteC5Coupe

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Any idea what this sound is. You can’t predict when it will happen. It will be two to four descending notes. Usually happens when I let off the gas. Listen to the sound in the following link. Kind of sounds like a cuckoo. https://photos.app.goo.gl/afKE2fcQaEvswg4d8


2015 - 2017 Expedition?

I have had the sound for quite some time on my 2015 Expedition Limited 4x4 (purchased new). It sounds like a moan or owl hoot - and sometimes it will sound like you described - descending notes.

Twice I’ve had it at the Ford dealer and they insist they cannot hear the sound

When I drive it (2WD or AWD) - the sound occurs when I lift the gas pedal. It can be heard with the windows up and the radio on. It sounds as though it is coming from the left front engine compartment.

On my own, I replaced the following with OEM Ford parts (in an attempt to eliminate the noise): degas bottle CAP, brake booster check valve, IWE check valve and hose assembly, IWE solenoid. None changed the noise.

About two years ago, the Ford dealer replaced the Degas bottle with a new one, due to a leak. I now suspect the bottle is what is making the unusual noise. The noise began after the Ford dealer replaced the engine water pump.

I’m hoping someone replies to this thread with a cause and repair?
 

99WhiteC5Coupe

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Cutest mechanical noise ever.


But very aggravating when my Expedition repeatedly has the noise and the Ford dealer cannot find the cause!

I’ve had passengers comment on the noise, telling me there is something wrong with my vehicle.
 

JasonH

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I know my previous response wasn't very helpful, lol. Maybe smoke test the system for leaks? I'm guessing the pressure release solenoid on the CAC because this sounds like a noise a blow-off valve would make. The rubber seal on those valves is known for tearing. Does the sound vary by acceleration rate? If you're accelerating quickly vs slowly, does the pitch or likelihood of hearing the noise change? That might provide a clue. Here's a video about the part:

 

99WhiteC5Coupe

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I know my previous response wasn't very helpful, lol. Maybe smoke test the system for leaks? I'm guessing the pressure release solenoid on the CAC because this sounds like a noise a blow-off valve would make. The rubber seal on those valves is known for tearing. Does the sound vary by acceleration rate? If you're accelerating quickly vs slowly, does the pitch or likelihood of hearing the noise change? That might provide a clue. Here's a video about the part:



Thanks for the ideas.

On my vehicle, the sound occurs at low engine RPM, but at various speeds. It never occurs while braking or during quick acceleration, only with a somewhat steady speed and when I lift my foot from the gas pedal.

I can start the vehicle and drive away slowly, and reach 20-25 mph, then lift the gas pedal as I approach a stop sign. The noise occurs.

I can be driving a steady 50-55 mph on a level roadway, and lift the gas pedal as I approach a red light (no brake apply). The noise occurs.

It also occurs at other speeds, but not during acceleration - only a steady speed then a pedal lift.

I did examine the blow off valve location and piping - and there appears to be no damage or breaks.

I’m leaning toward the degas bottle, as it is on the left side and high in the engine compartment - and when lifting the gas pedal, the RPM’s drop and cause a coolant surge.
 

JasonH

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RPM correlates with speed and gear, not throttle position. Try using a manual mode on the transmission so you can lock the RPM, then see if you can get the noise. It sounds like charge air is venting someplace when the throttle body slams shut.
 
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Louky

Louky

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Thanks everyone for the recommendations. I don't wish it on anybody, but it's good to know I'm not the only one experiencing it.

I just got back from a 1600 mile Florida trip. I doesn't seem to affect the performance, it's just kind of embarrassing when one of your passengers notices it. It did it the most when I was heading up the mountain north of Chattanooga.

I will be looking into the blow off valve and CAC. JasonH, thanks for the video link.
 
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