Unidentifiable Noise

[bavism]

I know this is vague, but I'm hoping someone might have some ideas of what I am hearing.

My exp is new to me, so I'm still getting aquainted with the noises I hear and haven't yet figured out 100% which ones are normal or just to be ignored.

Anyway on a couple of occasions when I'm accelerating at around the 15-30mph mark I will hear what sounds like a rush of wind coming from the passenger side either from the engine compartment or possible wheel area. I hear it for a couple seconds and it goes away without me changing anything (like taking my foot off the gas or tapping the brakes).

Is there anything under the hood that could kick in that may be responsible for the noise. It sounds like a fan has kicked on, but it is only there for a very short time. And not there with any regularity.

Any ideas?

 

[xtamer]

mine does something similar. almost like a whistle/humming noise. I assumed it was a vacuum leak.

 

[metaldrgn]

Mine doesn't do that. A video would help if possible

 

[ExpeditionAndy]

Mine doesn't do that either. What year is your Expedition?

 

[bavism]

Mine is a 2003. It happens so infrequently that it is difficult the isolate the cause.

I think though I've pretty much eliminated anything in the wheel. When the noise kicks in, I've tried turning my wheel to the left and right, tapped my brakes, started slowing down. None of these actions seem to affect the noise. I'm usually not in a place where it would be safe to come to a complete stop but that's my next goal. I would like to see if I come to a complete stop will the noise continue.

At first I just thought it was wind (and may turn out to be that) but the wind on a windy day beating against the sides and windows, sounds different.

I'll try to make a video as suggested, but it's going to be difficult catching it on a video because I usually only hear it 1 or twice a week. So having my phone ready to record (and to do it safely while driving) could be a challenge.

Matt

 

[bavism]

I've been able to determine the noise has something to do the the A/C. The sound is not always there when I have the A/C on, but I have figured out that if I shut off the A/C the noise stops. Then turn it back on and the noise will return. If the fan is on anything but the lowest setting, the noise from the blower covers up this mystery noise. So I suspect it actually makes this noise more regularly than I'm aware but is being hidden by the sound of the blower motor.

It only seems to make the noise mostly when I'm accelerating or have the engine around 2000 rpms. But it goes away within a few seconds.

Is there something about the A/C that would explain this noise. It's not getting worse, so I'm not concerned about it, but I would love to know what's causing it.

Matt

 

[ExpeditionAndy]

Could it possibly be a vacuum leak? It might get louder under acceration.

 

[toms89]

You may be hearing the compressor kicking on or off and the pressure differential occurring in the a/c freon lines?!

 

[toms89]

Could it possibly be a vacuum leak? It might get louder under acceration.

Manifold vacuum is strongest with the less throttle input. If you put your foot into manifold vacuum drops to near zero.

But there is a vacuum reservoir that operates the misc accessories and there is a check valve between the reservoir and the manifold so the accessories can still operate under low engine vacuum conditions.

 

[RAWPWR]

if the AC is on and is blowing out the upper dash vents, does it stop blowing out the dash vents when the noise happens?