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Thread: Doing some investigation to try and pin point knocking sound

  1. #1
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    Doing some investigation to try and pin point knocking sound

    as the title says. im going to take rocker cover off and check if push rods are straight and seated properly, and rockers are ok and lash caps.

    im scared that i may have made a soft spot on head when i first had it running after new head works. i was careful but ive been paranoid since i read some threads about similar issues.

    one thing i wanted to do was run engine with no rocker cover on to see if the noise is definately coming from there. if not obvious without cover on then can rule that out.

    so first question is:

    can the 300tdi run with the rocker cover off, even if just briefly just to listen? i would do it in a clean environment. for say 30 seconds. i know some engines spray oil all over the place but not sure bout 300tdi.

  2. #2
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    Go and buy yourself a stephoscope - can be really helpful.

    Tom.

    And yes, it will run with the rocker off.
    1996 Disco 1 300TDI manual - Lucille a cantankerous red head! :D
    1997 Disco 1 300TDI Auto - sold

  3. #3
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    Quote Originally Posted by BathurstTom View Post
    Go and buy yourself a stephoscope - can be really helpful.

    Tom.
    I've also seen mechanics using a long screwdriver to pinpoint source of odd engine noises - handle end near one ear and move blade end around area where noise is suspected to be coming from.
    Roger


  4. #4
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    Drillers do the same listening for lifters and the like to engage once they're run down the hole, screwdriver to the barrel.

    Sent from my HTC One using AULRO mobile app
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  5. #5
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    I tried the screwdriver trick. Didn't help much. The loud knock sounded loudest at IP.

    One of my push rods is very slightly bent. Don't think this is the cause though. Everything under there seemed fine.

    There's more oil than usual in the brather pipe and through intercooler pipe, also some coming out side of rocker cover, which i never used to get. The cyclonic cleaner wasn't too dirty though. I'm now fearful there may me combustion gases leaking from HG. I'm too paranoid to have a D1.

  6. #6
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    adjusted all the clearances again, number 3 was a bit tight, all the others pretty good. found an air filter in the cupboard so replaced the old one. cleaned out cyclonic cleaner and all the pipes for IC. certainly runs a lot smoother and turbo spools very nicely. the knocking has reduced a bit. might get a stethoscope to help pin point it more.

    will keep an eye on it for now. see if theres more oil than usual coming out. another thing i noticed is that the coolant in the expansion tank was a bit low. the engine saver hasnt gone off though. should i top up the coolant in exp tank to the marker? or is it normal for the levels to move around a bit?

  7. #7
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    just an add-on to the above. last time i played with IC hoses i couldnt get them tight enough and was getting leaking. you could hear it in the sound. now the turbo spools nicely with new filter but wondering whether there is some leaking.

    i have a boost gauge which measures from the inlet manifold. if there was a leak, would i see a drop in boost numbers there? i get the same numbers as before. ie. gets up to about 14psi under max boost. with any sort of leak this number would be much lower? or can you still have slight leak and get those numbers?

  8. #8
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    Fausto79, Just a note for you to remember when using a screwdriver.

    Place your thumb over the handle of the screwdriver, ie hold it like normal but run thumb over the end, so your thumb knuckle is where you push your ear against.

    This will take some of the raw noise out and you can hear knocks better, and that will assist with you finding where the knocking sound is the strongest. It wont take the sound of the journals or cam bearing noise away, but it will take general crappy sounds out..

    And on the knock, take the push rod out and test on glass. If its bent, replace. You may be able to straighten(not many will tho).

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    Quote Originally Posted by Fausto79 View Post
    just an add-on to the above. last time i played with IC hoses i couldnt get them tight enough and was getting leaking. you could hear it in the sound. now the turbo spools nicely with new filter but wondering whether there is some leaking.

    i have a boost gauge which measures from the inlet manifold. if there was a leak, would i see a drop in boost numbers there? i get the same numbers as before. ie. gets up to about 14psi under max boost. with any sort of leak this number would be much lower? or can you still have slight leak and get those numbers?

    A slight leak wont give you much to work on as the gauge would have to be in smaller increments and a base line to work on.. Not sure on your engine, but diesels show signs of leakage through knocking, sluggish, white smoke and sometimes black smoke too...

    Another sign of bad fuel burn is walking past exhaust, you'll feel a bitter feeling in your eyes, unburnt fuel, also another way of detecting fuel injector problem or glazing..

    Leakage causes over fueling, by a lack of air. aftercooler hoses can be sealed with sealants, but be careful and very sparing..

  10. #10
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    car barely smokes. i think fuelling is ok. id say probably no leak although it feels a little smoother it also feels a little less powerful if that makes sense. might just be my perception because it doesnt rattle as much when accelerating.

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