3.7 knock?

Discussion in 'KJ General Discussion' started by jeeptorino68, Jun 17, 2019.

  1. jeeptorino68

    jeeptorino68 Full Access Member

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    I have a rattle from the engine today after a weekend of camping and 4wheeling.
    3.7 with 223,000 miles. Regular oilchanges since ive owned it at 150k.

    Rattles at idle, kinda like some kind of loose metal or heat shield. And then goes away as I pick up engine rpms. Comes back around 1200 or 1500. Then I cant really hear if its still there. When you sharply let off the throttle you hear the rattle wind down...

    Could it be a bearing or rod knock?
     
  2. ltd02

    ltd02 Comfortably numb KJ Supporting Member

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    Is it coming from the bottom or top? If top, are you sure it isn't a pulley or tensioner from the serpentine belt drive? I had rod knock from a bad rod bearing in my 02 and it was a low knock, not even remotely like a rattle. Did you shake the exhaust from front to back?
     
  3. jeeptorino68

    jeeptorino68 Full Access Member

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    Sounds more bottom. I'm,investigating more. On the way home from work. It was less if none at idle. But more from 1500 rpm up. Odd...
     
  4. jeeptorino68

    jeeptorino68 Full Access Member

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    I think its more top end maybe...? Changed the oil, no change, went away at idle and is quieter at rpms, but when you let off the pedal to drop back to idle, it rattles. Nothing in the oil filter of any significance. No chucks or pieces. No glimmer in the oil either...

    Its not missing or running wiers either. Same fuel mileage as always. No coolant or oil loss either.
     
  5. Billwill

    Billwill Full Access Member

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    I had a rattle after going through some rough stuff.

    Was a stone logged between the front diff and the skid pan on my 2002 Export CRD.
     
  6. jeeptorino68

    jeeptorino68 Full Access Member

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    Its just really inconsistent though...
     
  7. GeekFisher

    GeekFisher Full Access Member

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    My 03 is doing that when cold. Likely a loose heatshield. Look for them down the exhaust pipe.
     
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  8. jeeptorino68

    jeeptorino68 Full Access Member

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    Well its not the drive belt. Or any of the pulleys and bearings. Took the fan and belt off, the noise remains. Seems more top end the more I am listening around.
    Could it be a failing hydraulic lifter? What could I see or look for if I remove the valve cover(s)
     
  9. jeeptorino68

    jeeptorino68 Full Access Member

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  10. ltd02

    ltd02 Comfortably numb KJ Supporting Member

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    Sounds like a very good possibility. If I heard it in person I'd probably be able to tell you for sure. With that many miles and them being hydraulic, I wouldn't be surprised. I had one fail on my 02 but never really chattered much. Threw the rocker twice and changed it the second time. Only other thing could be some timing chain chatter (hydraulic tensioner). Would be more from the front of course.

    Not really sure about what you'd see by a visual inspection though.
     
  11. jeeptorino68

    jeeptorino68 Full Access Member

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    It definitely isnt front of engine. With the fan and belt off I was able to get my ears close. Sure seems to be the top end...
     
  12. ltd02

    ltd02 Comfortably numb KJ Supporting Member

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    Unfortunately it's tough to tell anything about the lash adjusters by looking. If one collapsed and doesn't pump up fully it'll rattle (until the rocker falls off). I remember when I removed my bad one it could not be compressed anymore even in a vice. I'm not a mechanic but If it were good I believe you would be able to compress it in a vice and oil would ooze out.The new one was moveable dry but should stiffen when it fills with oil (still extended). The Melling I got specified that it wasn't necessary to soak them prior to install.
     
  13. jeeptorino68

    jeeptorino68 Full Access Member

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    Thabks for the advice
     
  14. jeeptorino68

    jeeptorino68 Full Access Member

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    Ok, well ordered a set of lash adjusters and valve cover gaskets, will take it apart soon when parts are in thier way. Not sure what else this could be....

    Any other things to do while I'm in there?
     
  15. mrlavalamp

    mrlavalamp Full Access Member

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    inspect everything you can while you are in there.

    Look for mushrooming on the heads of each valve stem, wear on the camshaft lobes, slop in bearings, broken springs, and I am sure there is more I am forgetting.
     
  16. jeeptorino68

    jeeptorino68 Full Access Member

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    Well it wasnt lash adjusters. Same noise before and after. The top end looked great. No issues on the cam. Springs. Rockers. Etc.
    I guess its something else..
    I'll keep looking...
     
  17. jeeptorino68

    jeeptorino68 Full Access Member

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    Still not finding much, was under the jeep,while my wife ran the engine. Heard the most noise back by cylinder 6, but could be the pre cat on that side too maybe???
    I unplugged cool packs one at a time yesterday and got no notocable change in the noise. Some change but alight
    Will drain the oil tonight and see if there are any flakes. If not that rules out bearings I think
     
  18. ltd02

    ltd02 Comfortably numb KJ Supporting Member

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    Have you ruled out an exhaust leak?
     
  19. jeeptorino68

    jeeptorino68 Full Access Member

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    no...but its such a rattle, I have never heard an exhaust leak like that before... I can check for that though...if the guts in the pre-cat were bad...that might cause all this rattling?
     
  20. ltd02

    ltd02 Comfortably numb KJ Supporting Member

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    I've had cats disintegrate and rattle. That was a long time ago though.