weird vacuum sound from under hood.


Active LVC Member
Aug 11, 2011
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this sound is very loud and to me sounds like a vacuum. to me it seems like it is coming from somewhere on the passenger side. i was wondering if anyone could tell me possibly what is causing the sound and/or how to fix. i took a video so you could hear it.

PCV elbow if a v6? Any CEL's? I had a similar issue and it was coming from a vacuum hose deep at the top back of the engine. Just start pushing stuff together until you notice a difference in sound.
It's a 06 v8. No cel. Pressing the gas pedal u hear it louder. Then once back at idle speed it does it again.
It's a 06 v8. No cel. Pressing the gas pedal u hear it louder. Then once back at idle speed it does it again.

A vacuum noise should be reduced while accelerating.
Could it be the fan, or a bearing on one of the idlers?
Yeah can't figure it out so a trip to the stealership is what is going to happen monday
try and see if you can get them to agree that they first "possibly" try re&re serpentine belt, idler pulley, see if that clears it up before letting them sell you a new coolant pump or other accessories running off that belt. That's at least the route I would first want to try.
Sounds like bearing to me too. Before spending at the dealer I'd pull the accessory belt off. Start the car to see if the noise is still present. You only want to run it a few seconds without the belt because the water pump won't be spinning. If the noise is still present it rules out all accessories and points to a serious problem. If the noise is not present (and I think it will be gone) then you can spin each accessory on the belt by hand. As loud as it is, you should be able to hear the offending component with a hand spin, or at least feel the drag in your fingers. A good accessory will feel smooth when you spin it, a bad one will feel rough and will likely squeak. I'm going to say alternator from the noise. If you still can't isolate it, you can still take it in but this might save you a few bucks.
I know its a been a few years but is this what a failing alternator or water pump sounds like?

Just got this same loud vacuum cleaner noise last night after a long drive. On cold start sounds horrible. After warm up later its 98% gone. Feel like its in the middle to passenger side.

Replaced my idler and tensioner last year. If I recall alternator and compressor pulley doesnt spin freely as there is resistance so taking belt off wont really help. Dont think there is enough room to try the screwdriver test..
Failing alternators can make some strange sounds. I don't know that I would call any of them vacuum cleaner sounds (certainly wouldn't call any vacuum leak sounds), but we all describe things differently.

Put a good volt meter on it and drive it around. The voltage should be a bit off when it is making the noise, if this is your problem.

The LS has the least fun alternator the change of any that I have changed. Try to be sure before you go after it.
As long as I dont have to take the coolant system apart again...

Honestly, I'd rather change all the cooling system plastics (except the radiator) than change the alternator again.
As long as I dont have to take the coolant system apart again...
I had a professional change out my alternator ...I agree 100% heck 110% that changing this cars alternator is a major PITA I remember the mechanic had to remove some parts to get at it not sure what but some other ppl on the site could probably tell you...I suggest allowing a pro do this job
The manual says its not to bad. Only says remove shield/pan then wiggle out. Hope its not that much of a pain nor my alternator. Although my other candidates arent any easier..
There's a lot of manuals out there like that.

Step 1, remove engine.

Step 2, remove alternator.

The alternator on an '03 Escape is no joy either.

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