Guess the source of my Knock

Discussion in '6.9L IH & 7.3L IDI Diesels' started by Vanzal15, Jun 25, 2018.

  1. Vanzal15

    Vanzal15 Registered User

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    The SOUND:

    Hints:
    1. Started while leaving work and got progressively louder on my 30 minute 12 mile commute home.
    2. Shakes the cab a bit.
    3. Filled both tanks with diesel 5 miles before work.
    4. 200k miles on motor.

    Post up your guesses. I'll probably start the investigation next weekend.
     
  2. 79jasper

    79jasper Chickenhawk

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    Rod, knock knock knocking on heavens door.

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  3. jwalterus

    jwalterus Made in America

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    I'm going to guess from your description of events that your "diesel" you topped off with was a little high in Ethanol content, maybe about 10%?
    In other words, give your fuel a sniff test because I think you got RUG instead.........
     
  4. tjsea

    tjsea Full Access Member

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    I second possible gasoline instead of diesel. Would make sense since you just filled it up. Otherwise I'd start looking to valve issues. It almost sounds like its coming through the intake.
     
  5. IDIBRONCO

    IDIBRONCO IDIBRONCO

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    That's my guess too. You almost never hear of a spun bearing on one of these engines without extreme circumstances. It seems to be almost common on the GM 6.2/6.5 engines.
     
  6. Joseph Davis

    Joseph Davis Full Access Member

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    Wow now that is a loud knock, dead cylinder with valve hitting piston? you still have screen on throttle body? lol, Well sorry for the bad luck. I hope it is something simple.
     
  7. Ethan Smith

    Ethan Smith Full Access Member

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    Shit that sounds like me hitting my head into the wall when the wifes bitching at me
     
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  8. Garbage_Mechan

    Garbage_Mechan Garbage Mechanic

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    You guys are silly. That ain’t a knock. It’s a valve issue. Popping back into the intake.
     
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  9. Garbage_Mechan

    Garbage_Mechan Garbage Mechanic

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    Either something is keeping the intake valve from sealing ( bent, sticking, bad guide, weak or broken spring) or the exhaust isn’t getting out because of an exhaust valve issue (broken rocker, bent pushrods, lifter or cam issue)
    When the exhaust valve isn’t opening the trapped air comes back out the intake when it opens. I would guess the intake.
     
  10. Macrobb

    Macrobb Full Access Member

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    Pull valve cover, look for loose rocker or bent pushrod. Mind you, a pushrod would have to be very bent to cause thumping like this; it's not a "this pushrod isn't flat within .005"" type issue - it'd be blatently obvious.
     
  11. Vanzal15

    Vanzal15 Registered User

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    Yall, thanks for the ideas. I decided to take a moon shot and fill the fuel filter with fresh diesel form a "trusted" gas station. I fired the old girl up and let her idle for 1 minute. no improvement. The GF is whining i don't spend enough time with her so I promised i would take her floating on Saturday. Right now i got Sunday in my crosshairs to take the valve covers of and see what i can find. Pix to follow.
     
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  12. Vanzal15

    Vanzal15 Registered User

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    Found it.....

    Rod is not bent. Rocker is not bent. Spring does not appear to be broken.... If I angle the rod into it's hole it catches on a higher and lower surface. Is it possible it is slipping off the lobe on the cam?

    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]


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  13. 79jasper

    79jasper Chickenhawk

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    The push rod doesnt engage the cam directly.
    Sounds like a collapsed lifter.

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  14. Vanzal15

    Vanzal15 Registered User

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    What do you know about the surface/connection between the lifter and rod 79? Both the "good side" and bad side of that piston's valves have angles at which I can insert the rod that it goes in much deeper. Not sure if there is a small pocket on the lifter that the rod fits inside and if you miss the pocket the rods slips deeper or what.... Hope that makes sense. I'd imagine its impossible to remove the lifters from the top of the block after the head is removed? If it's rebuild time I'd likely take a few months to rebuild and upgrade this thing. If I can patch it for a few months though that would be ideal as I'm doing a bunch of landscaping and house work that I was counting on using the truck for.


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  15. 79jasper

    79jasper Chickenhawk

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    Maybe this pic will help. No need to remove the head. [​IMG]

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