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Thread: Whistling noise from the engine

  1. #1
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    Whistling noise from the engine

    Hello Forum,

    This is my first time posting, so apologies if I leave any vital information out. I have an '04 325i sedan. Recently I have been hearing a whistling noise from the engine. It's especially apparent when I step on the gas from a stop. the higher I rev it the louder the whistling.

    Anyone ever encountered this? I don't want something small to turn into something major because I failed to get it checked out; any shops you guys would recommend in the Bay Area?

    Thanks!

  2. #2
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    First thing I would check for is a tear in your intake boots. Even a small crack can make a whisling sound. Other than that, I really don't know enough to confidently troubleshoot anything. I'm sure someone else will chime in.

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  3. #3
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    Thanks! I appreciate it!

  4. #4
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    If you can, post a video of the whistle sound so we can better diagnos.

  5. #5
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    Try to isolate the sound within the engine bay. I'm leaning toward pulleys/belts since you don't have an SES light.

    The higher you rev, the louder it gets. Makes sense.

    So...in short....inspect your pullies.

    [ame]http://www.youtube.com/watch?v=3jJgZgCJhvQ&feature=youtube_gdata_player[/ame]

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    Last edited by danewilson77; 09-19-2012 at 08:21 AM.

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  6. #6
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    I'm gonna say pulleys too. They can change their noise under different circumstances. This is a pretty simple fix. Easier of you have a manual but still easy if you have an auto.

  7. #7
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    +1 on pulleys

  8. #8
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    For my a pulley would be a squeak or a whine. A whistle noise is most definitely the intake boot either having a crack in it or not seating properly on the intake box (or intake filter if you have a CAI at some point).


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  9. #9
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    Either way, both intake boots and pulleys are easy to check for. But FWIW, I've had both go bad in the last year and my pulleys were only audible at idle and was more of a squeak. My intake boots however was definitely a whistle and they were almost completely torn in half, yet I had no SES light...
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  10. #10
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    I have a 2003 325i and this recently happened to me. I had to replace my idle stabilizer bearing and this might be your problem

  11. #11
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    Thanks for all the input!

    From what it sounds like I am either looking at a problem with the pulleys or the intake boot. Does anyone have any shops in the Bay Area they would recommend? Thanks again guys.

  12. #12
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    Pro tip: get a rubber or plastic hose, about an inch in diameter put one end on your ear and move the other end around the bay till you pinpoint the location of the sound. Home made stethoscope, works everything.

    Sidenote: I would really lean towards the tensioner pulley , really easy to do.

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  13. #13
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    pro tip..

    putting a flimsy tube around moving parts is not a good idea if youre unfamiliar with the car. the belts or fan can suck that in and cause more damage.

  14. #14
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    i had a little of a whistle from something that had to do with the throttle, im lost for words someone might be able to help me but moral of the story is my mechanic said its normal and it just happens overtime but doesn't cause any harm.

  15. #15
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    I am betting on a hole in the flexible part of the intake boot at the throttle. My car is torn there and I get a ses lamp sometimes other times not. whistling is so loud at different throttle postitions that I can hear in car.

    pulleys will also make noise but will change pitch and intensity at different speeds or go away all together when throttle is applied.
    Level 1 Certified BMW tech.

  16. #16
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    I have the same issue, there was definitely a crack in the intake boot. Dealer replaced the boot. I still have a whistle between 1500 & 2500 rpm. Haven't been able to narrow it down yet. My idler pulley & both belt tensioners were just replaced because of horrible noises coming from them, but it wasn't the cause of the whistle...

  17. #17
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    might be the bearings in the alternator. mine were bad.

    might also be the AC tensioner.

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