W202 C43 AMG Very wierd humming noise

Discussion in 'Engine' started by porterada, Mar 24, 2014.

  1. porterada

    porterada New Member

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    Hi Guys,

    Im new to the forum to excuse me if this has been put in the wrong section. I have a very very strange Humming noise that has developed on my lovely C43. This has only just started in the last week or so. What happens is that most of the time when i drive it now after i hit 30 or 40 mph i start to hear a humming noise coming from the engine bay. it does not change pitch with rpm or road speend and makes the noise when in every gear, and even if i shift to Neutral. the noise is the same regardless of how i am driving. When i pull up say at a set of lights etc, after a few seconds the noise stops. Recently i have had both Lower wishbones replaced but i think this is just a Coincidence. The car had a B service in December which included Tranny oil replace.
    To me the sound is too light to be anything metalic. its almost like a hum/buzz sound.

    Just wondered if anyone has come across this?
     
  2. BlackC55

    BlackC55 Authorised Forum Sponsor Authorised Forum Sponsor

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    Could it be worn engine mounts?
     
  3. guydewdney

    guydewdney Hardcore MB Enthusiast

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    If it doesnt change with engine speed or road speed, then could it be the fan? Both the engine and the interior blower? Air con fan being blown around? Turn aircon on and off and int fan on and off?
     
  4. OP
    OP
    porterada

    porterada New Member

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    Hi Thanks for your reply, I have tested with fan/ aircon on off, the weird thing is, most of the time when i pull up after a few seconds the noise stops but sometimes it does not. When it has not stopped if i turn the car off then back on the noise goes, . I am lost with this one As if it was gearbox i would expect it to stop or change pitch if either with driving different or moving selector. it’s almost like the sound of a vacuum leak but it’s so intermittent i am totally lost.
     
  5. OP
    OP
    porterada

    porterada New Member

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  6. Stratman

    Stratman Hardcore MB Enthusiast

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    Could it be the tiny fan in the overhead console, the one that draws in cabin air to measure its temperature?
     
  7. OP
    OP
    porterada

    porterada New Member

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    I did not even know that the c43 had one :( i have been trying to pinpoint where the noise is coming from and its either near the bulkhead or under the front. :( I hope its not gearbox starting to give :(
     
  8. guydewdney

    guydewdney Hardcore MB Enthusiast

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    Use a tube shoved in your ear to locate the sound?
     
  9. ricardo62

    ricardo62 Hardcore MB Enthusiast

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    what you mean an ear trumpet ?
     
  10. LexCorp

    LexCorp New Member

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    Have you actually checked under the bonnet when the car is making this sound? I sounds like an egr or throttle valve actuator
     
    Last edited: Mar 25, 2014
  11. OP
    OP
    porterada

    porterada New Member

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    Yep Been under the bonnet, To me it sounds like the noise is coming from the lower back of the engine bay. :( almost under the car. i thought originally maybe it was alternator or anything else which is on the poly belt but it seems to be coming from the oppisite end, IE bulk head area i cannot seem to pinpoint exactly where it is coming from.
     
    Last edited: Mar 25, 2014
  12. Sp!ke

    Sp!ke Administrator Staff Member

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    I had a similar noise on my W124 - drove me bananas for a long time trying to track it down.

    It turned out to be an engine mount.
     
  13. BlackC55

    BlackC55 Authorised Forum Sponsor Authorised Forum Sponsor

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    Pop it up to me for a listen. I probably know 43's better than anything
     
  14. guydewdney

    guydewdney Hardcore MB Enthusiast

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    theres several vacuum things that can make some slightly odd drrrrr noises after engine switch off that are generic I suspect. Im sure mine makes this noise from around the brake solenoid area - sounds almost like a tiny burp but for about a minute.
     
  15. horgantrevor

    horgantrevor Hardcore MB Enthusiast

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    I think it may be the sniffer fan look up at front light switch and sunroof switch look for a circular opening with slots in it about the size of a pound
    Behind that is a little electric fan with a plastic fan on it they can cause this

    I had the same it drove me mad till I sorted it one day easy fix all the w202 facelift have one so you should pick one up easy
     
  16. guydewdney

    guydewdney Hardcore MB Enthusiast

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    your engine temp looks a tad high.
     
  17. The _Don

    The _Don Hardcore MB Enthusiast

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    Nope that's normal.
     
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