loud knock on startup 12.7 detroit

Discussion in 'Freightliner Forum' started by ptwn1, Mar 27, 2013.

  1. ptwn1

    ptwn1 Light Load Member

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    Oct 4, 2012
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    hi my truck makes this loud knocking sound during startup when the rpms settle down to around 500 rpm. when i press the gas it gets louder, after 1000 rpm it goes away and after i run it for a while it will go away. this only happened to me three times so far. any help pls
     
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  3. Smellfunny

    Smellfunny Road Train Member

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    Jan 28, 2012
    South Carolina
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    COULD (emphasis on COULD) be an injector. Need someone to hook up to it when it is first started and see what is going on.
     
  4. WitchingHour

    WitchingHour Road Train Member

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    It might be your piston rings.
     
  5. goranvolvo

    goranvolvo Bobtail Member

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    Mar 2, 2013
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    it is normal on coold detroit
     
  6. megastang

    megastang Bobtail Member

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    Feb 27, 2013
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    I was going to say the same thing
     
  7. Cowpie1

    Cowpie1 Road Train Member

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    Kellogg, IA
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    I would agree with that. Especially in the colder time of the year. My factory rebuilt 12.7 has done this in winter months after sitting for quite a while, unplugged, and then started. When still slightly warm or when plugged in on a cold night, it doesn't do it. Previous Series 60's I have been around did the same thing.
     
  8. Hanadarko

    Hanadarko Independent Owner/Operator

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    Midwest
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    What was the starting temp when this sound happened?

    If I start my S60 engine around below 15F outside, she can tend to make all sorts of obnoxious noises.
    They tend to clang around until they settle out, but I never give it fuel...just let it chug along until it smooths out.
     
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