Diesel knock - what else to do





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  1. #1
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    Angry Diesel knock - what else to do

    After refurbishing the injectors, blanking the EGR and removing the CAT my bakkie is a lot more responsive and almost 1.5km/l better on fuel consumption. But, the annoying diesel knock is still there when it is cold! Not only in the morning, any time that I drive with it when cold it sounds like a tank and is underpowered for known reasons. What else can I do/change/replace? It is worse if I use any diesel other than Sasol 10ppm.
    n' profeet word nie in sy eie land geken nie!

  2. #2
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    Default Re: Diesel knock - what else to do

    What bakkie is it?

    Check the temp sensor that its working properly, it may be giving a reading lower than normal, hence the overfueling/knock/unburnt diesel.

    Or, I hate to say it you don't have full compression when cold. As the parts get hot they expand and you get better compression.

  3. #3
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    Default Re: Diesel knock - what else to do

    Is n Isuzu nie "direct injection" nie?

    Toyota Land Cruiser 79 DC V8
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  4. #4
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    Default Re: Diesel knock - what else to do

    2011 KB300 DTeq
    n' profeet word nie in sy eie land geken nie!

  5. #5
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    Default Re: Diesel knock - what else to do

    check your diesel pump timing

    check for cracked fuel lines

  6. #6
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    Default Re: Diesel knock - what else to do

    A diesel knock that seems to get better or less noisy when the car heats up could be a cracked or broken piston.
    Leon 2005 Defender D/C CSW

  7. #7
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    Default Re: Diesel knock - what else to do

    Quote Originally Posted by LEON disco View Post
    A diesel knock that seems to get better or less noisy when the car heats up could be a cracked or broken piston.
    I guess the only way to find this out is to open everything up!
    n' profeet word nie in sy eie land geken nie!

  8. #8
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    Default Re: Diesel knock - what else to do

    Could it be so severe if there is no smoke on start up or accaleration? Consumption very good and uses no oil.
    n' profeet word nie in sy eie land geken nie!

  9. #9
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    Default Re: Diesel knock - what else to do

    Removed the dipstick, whitish smoke coming out when idling, is that the death wish?
    n' profeet word nie in sy eie land geken nie!

  10. #10
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    Default Re: Diesel knock - what else to do

    Not necessarily, sounds like oil mist. Even some petrol motors mist oil.

  11. #11
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    Default Re: Diesel knock - what else to do

    It's an Isuzu diesel. If you worried get a compression test done. That noise is probably your tappits,get them reset.
    Isuzu STD 2.5d 2x4 rear diffy lock
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  12. #12
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    Default Re: Diesel knock - what else to do

    my two cents worth..i owned a Discovery TD5 which had a slight diesel knock,poured in some prolong and knock was much less and motor more smooth..

  13. #13
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    Default Re: Diesel knock - what else to do

    On my Isuzu 280 I had a thermostat that was stuck slightly in the open position. Also had a diesel knock, because the fuel pump advances the timing if the coolant is cold.
    98 Hilux 2.8D D/C 4x4

  14. #14
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    Default Re: Diesel knock - what else to do

    Quote Originally Posted by Pottie1 View Post
    2011 KB300 DTeq
    Pottie - ek het ook 'n 2011, met dieslefde geknock- standaard. Sedert 23000km het die bakkie dit net wintersoggende gehad. Nou op 105000km met elke koue start. Sodra die hittemeter op "kwart" is, "purr" sy soos 'n kat!

    Uiters irriterend - ek verstaan jou pyn!


    Ek het ook al Liqui Moli se anti knock gebruik, met geen resultate.

    Bostoe
    Last edited by bostoe; 2018/08/26 at 11:34 AM.

  15. #15
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    Default Re: Diesel knock - what else to do

    Quote Originally Posted by Pottie1 View Post
    Could it be so severe if there is no smoke on start up or accaleration? Consumption very good and uses no oil.
    Selfde hier. Twyfel of dit 'n cracked piston is.

    Bostoe

  16. #16
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    Default Re: Diesel knock - what else to do

    Maybe worth posting a video or sound clip. Too much pump timing can cause horrible and damaging knock. But Isuzu has always had a fairly "knocky" engine. When my Nissan "pre ignites", I can feel it in the car, and its more a banging sound than knocking. I've never had a diesel knock, but managed a few times to get pre ignition when I get my HHO or petrol gassification injection wrong, and there is some residual mix in the intake at startup. It goes off with a horrible bang.
    David/Hillbilly - 1997 SFA Nissan Sani 2,7 TD - 5" lift on 33" tires - Dual Transfer with 4.1 gears

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  17. #17
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    Default Re: Diesel knock - what else to do

    Could be leaky injectors dumping a small amount of diesel onto the top of the piston after the engine has cooled down?
    2012 Jeep Sahara Unlimited 3.6 V6
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  18. #18
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    Default Re: Diesel knock - what else to do

    Appreciate the feedback! I did not sleep well this weekend due to the idea that I might have a cracked piston! I will have a compression test done first and start from there to try and solve this. I can live with the noise when cold as long as I know it is not going to blow soon. Any suggestions on where in Pta/Centurion I can have it done?
    n' profeet word nie in sy eie land geken nie!

  19. #19
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    Default Re: Diesel knock - what else to do

    Bostoe, dit is presies wat myne doen, sodra hy by "kwart" kom klink hy 100% reg.
    n' profeet word nie in sy eie land geken nie!

  20. #20
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    Default Re: Diesel knock - what else to do

    Quote Originally Posted by Pottie1 View Post
    Appreciate the feedback! I did not sleep well this weekend due to the idea that I might have a cracked piston! I will have a compression test done first and start from there to try and solve this. I can live with the noise when cold as long as I know it is not going to blow soon. Any suggestions on where in Pta/Centurion I can have it done?
    I think opening the bonnet and starting it while recording a video or a sound clip. Then uploading it to youtube and sharing the link would be good idea.Most of our isuzu's sound like tractors when they are cold around here.

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