diesel knock update

Discussion in 'Engine' started by runningman, Apr 29, 2014.

  1. runningman

    runningman Member

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    Hi

    Ive posted a number of threads over the past week with regards to my 1998 300 td, 606 engine.

    the engine is still knocking. ive replaced all the fuel lines and filters, used a thicker oil (10w 40) and hydraulic lifter treatment, had injectors refurbished and checked all auxiliaries. im now considering a faulty lifter is this a big job to do, im very handy with the spanners. Is there anything I should look out for that may cause me trouble.

    Regards
     
  2. E270 Owner

    E270 Owner Hardcore MB Enthusiast

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    I would pull the sump off and inspect the piston skirts, might be piston slap.

    Post a sound clip on here.
     
  3. OP
    OP
    runningman

    runningman Member

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    this knock just suddenly developed when it wouldn't start one morning, my dad said when he went to start it, it sounded like it was running on 2 cylinders and the engine was being hit with a hammer. Prior to that the glow plug came on intermittently but it ran perfect, smooth as silk.
    Couple days later we change the glow plugs, started first time but its knocked ever since.
    knocks at idle and 1250 rpm but when you rev the engine the knocking disappears, let the rev fall and knock returns at 1250 and back at idle.
    I cant think of anything else except for a faulty lifter.
    My dad did say at the very beginning that to him it sounded like a hydraulic lifter. He thinks it may have cause some damage that morning when it wouldn't start.
    Did you read my previous post from last week to get whole story.
     
  4. Dieselman

    Dieselman Banned

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    As the knock is only present when fuel is being injected the noise will be fuel related.
     
  5. E270 Owner

    E270 Owner Hardcore MB Enthusiast

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    TBH I shouldn't have replied ..........

    I don't usually when someone starts so many fragmented threads,

    It causes the wrong advice to be given.
     
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  6. OP
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    runningman

    runningman Member

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    E 270 owner. im new to this forum community and im only looking for some advice.
     
  7. OP
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    runningman

    runningman Member

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    is there a chance that the pump timing has slipped?
     
  8. johnsco

    johnsco Hardcore MB Enthusiast

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    Unless you've had it apart. it's unlikely that the IP timing has slipped.
    Referring to your previous threads - This is a low-mileage engine.
    These engines a pretty-much bomb-proof.

    I doubt that rough-running, bad-starting on only half the cylinders, cranking the nuts off it ..... or anything else that you have done to it can have damaged the piston- skirts, the IP or much else.

    I have done all these things to 606 engines (and worse) and they carry on running.

    Some sort of fueling or air in the fuel problem is most-likely.
    The fact that it runs smoothly at higher revs (and presumably on full power) says there can't be much fundamentally wrong with it.

    I could be wrong ... But that's how I see it.
     
  9. OP
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    runningman

    runningman Member

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    Is it possible that modern day diesel fuel with their additives could lead to degradation of the internal fuel pump seals? If so could this cause the pump to reduce fuel pressure to the injectors?, hence why it knocks at idle and round about 1250 rpm.
    Im exploring all the possibilities I can think of before I strip out the hydraulic lifters or adjust pump timing.
    Also when engine is switched off you can see the fuel run back an inch or two in the clear pipe line which delivers fuel to the filter. Engine starts first time every morning.
    When you hold the engine at say 2000 rpm you can see air bubbles travelling along the bottom most fuel line on the pump. :wallbash:
     

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