Hissing noise after switch off - 07 320CDI Diesel Esate

Discussion in 'Engine' started by ramer, Apr 22, 2013.

  1. ramer

    ramer New Member

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    Car:
    1995, E320 Estate
    Noticed recently, that after turning the engine off, there is a hissing noise from somewhere under the bonnet that lasts for about 15 seconds, then dies away over 3-4 seconds. Sometimes think I can hear it randomly inside the car when driving, again last for maybe 20 seconds then fades. No other apparent symptoms, no liquids appearing anywhere - any ideas???

    By the way, which "w" variant engine am I likely to have?

    Thanks.
     
  2. Tinkerer

    Tinkerer Active Member

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    Do you have the aircon turned on? this can usually be heard hissing through the vents.
     
  3. OP
    OP
    ramer

    ramer New Member

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    Aircon IS turned on, but it's much more like the hissing of a radiator or punctured tyre, neither of which it appears to be.

    I can imagine it might be some sort of leak from the Air Con, but there are no smells or odours at all, and you can hear the same sound standing next to the wing/bonnet.
     
  4. GordonTarling

    GordonTarling MB Enthusiast

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    The sound is from the aircon - it will hiss for a short while after stopping. Your car is an S211, with v6 engine (OM642).
     
    Last edited: Apr 22, 2013
  5. OP
    OP
    ramer

    ramer New Member

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    And I assume from what you're saying that's normal?

    Thx re the S211 info.
     
  6. b1g1an

    b1g1an MB Enthusiast

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    Really, I've had cars with aircon for thirty years and never heard any hissing like that.

    I'd assumed it was the SBC releasing the pressure.
     
  7. SL300-24

    SL300-24 MB Enthusiast

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    I think there is no SBC on a 2007 car.......
     
  8. b1g1an

    b1g1an MB Enthusiast

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    Good point, my other thought on mine was the air suspension but am only guessing.
     
  9. DRBC43AMG

    DRBC43AMG MB Enthusiast

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    You have a snake living under the bonnet...
     
  10. sspeed

    sspeed MB Enthusiast

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    Neither have I !
     
  11. developer

    developer MB Enthusiast

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    Does the car have Airmatic, identified with a switch behind the gearstick, as per the photo?
    [​IMG]
     
  12. OP
    OP
    ramer

    ramer New Member

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    No, definitely no switch like that behind the gear-selector....
     
  13. GordonTarling

    GordonTarling MB Enthusiast

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    Yes, quite normal. I used to hear it often on my 'old' 211, but not so noticeable on the current 211.
     
  14. b1g1an

    b1g1an MB Enthusiast

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    What is it though, mine does it when I lock it and coincides with the suspension lowering if it was set high/soft.
     
  15. developer

    developer MB Enthusiast

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    As does mine.
     
  16. OP
    OP
    ramer

    ramer New Member

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    No Airmatic (as far I know!) on my car, so it's not that...
     
  17. Charlie87

    Charlie87 Active Member

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    Mine does this aswel, 2008 S320, I assumed it was the air suspension exhausting excess pressure?
     
  18. Ian Donkin

    Ian Donkin Active Member

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    Off topic I know, but what is that wheel control for to the passenger side of your (stop/start) gear lever?

    Cracking spec'd car John :)
     
  19. Mark68

    Mark68 New Member

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    My S211 does the same thing, at the front. I'm fairly sure it's the air suspension.

    Mind you, I've been told that it shouldn't do it and it may indicate that I have a problem with the airmatic.....
     
  20. developer

    developer MB Enthusiast

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    Sorry Ian, I missed this - it's the Distronic thumbwheel for setting the distance from the vehicle in front - the car then maintains this distance as other vehicles enter/leave the radar beam.
     
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