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camshaft markings/valve timing

Discussion in 'Gen 3 Prius Main Forum' started by donzoh1, Feb 2, 2019.

  1. donzoh1

    donzoh1 Active Member

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    P.S. I can also see that the small hook has sprung open toward the timing chain cover. When tight, the top segment of the chain rubs against the upper chain guide but some slack remains depending on cam position.
     
  2. Mendel Leisk

    Mendel Leisk Senior Member

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    You've watched around the 33 minute mark, in that video?
     
  3. ChapmanF

    ChapmanF Senior Member

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    I remember the video (maybe around the 33 minute mark) suggesting the tensioner gets the benefit of oil pressure behind it once the engine starts, in addition to its own spring, and the chain might sound a little slappy for a few seconds until that happens. Maybe the oil pressure will be enough to extend it one more click.
     
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  4. cnc97

    cnc97 Senior Member

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    The oil pressure will finish tensioning the chain on startup. It might move a couple clicks when fully pressurized initially.
     
  5. ChapmanF

    ChapmanF Senior Member

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    Kind of a clever design, that. They could accomplish the same thing just by making the spring stiff enough inside the tensioner, but then it'd be really hard to install by hand.
     
  6. donzoh1

    donzoh1 Active Member

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    I see it as more of a design problem. Maybe it's not enough to damage anything. But, if a stiffer spring was used, it could be compressed with a vise or channel lock pliers. Or how about just a little more access in the timing cover where the tensioner is located? I'm guessing it's not enough to skip a tooth but that's the problem...I'm guessing.
     
  7. cnc97

    cnc97 Senior Member

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    If you want to be “sure” the chain won’t jump on initial startup, you can take a moderate size screwdriver and push toward the exhaust cam gear on the top of the tensioner. But as long as you can not lift the chain off the gear, it’s not loose enough to jump off the gear.

    That’s where the multiple rotations of the crankshaft come in. The tensioner provides a constant amount of spring pressure. The rotations ensure that all the slack gets taken out by the moving guide.
     
  8. donzoh1

    donzoh1 Active Member

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    I have done multiple crankshaft rotations and i dont think the chain has enough slack to jump. I'm not understanding where you recommend pressing with a screwdriver though.
     
  9. cnc97

    cnc97 Senior Member

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    Anywhere in the circled area in this photo. Gently pry the guide toward the chain. Listen for the tensioner to click. If you get one or two clicks out of it, you will be good.
     

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    #29 cnc97, Feb 9, 2019
    Last edited: Feb 9, 2019
  10. Gasketblower

    Gasketblower Junior Member

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    I have question is the Crank shaft sprocket suppose to be all loose when there is no chain on it what is holding it in position other then the chain because mine comes in and out freely and I wonder if thats what making the rattling noise I am hearing!
     
  11. cnc97

    cnc97 Senior Member

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    The sprocket is only free to move while the balancer is not installed. One you install the harmonic balancer, the crank sprocket can no longer move in and out.
     
  12. Mendel Leisk

    Mendel Leisk Senior Member

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    Looks like crank shaft sprocket is restrained from rotating on end of crank shaft by woodruff-style keys, but free to move fore and aft.

    upload_2021-7-29_7-42-9.png
     
    #32 Mendel Leisk, Jul 29, 2021
    Last edited: Jul 29, 2021
  13. ChapmanF

    ChapmanF Senior Member

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    I doubt it has any fore-and-aft axial motion once the crankshaft pulley (or 'balancer', though it's still pulley-shaped even in beltless Gen 3) is installed and torqued down.
     
  14. RobBlak_2010_Prius

    RobBlak_2010_Prius New Member

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    Did this video get removed?
     
  15. Mendel Leisk

    Mendel Leisk Senior Member

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    Yes. Seems like gasket masters YouTube channel devolved into infomercials, they took down the good ones. I have some of them salted away, but don’t want to cross copyright boundaries. :(
     
  16. prius-07

    prius-07 Junior Member

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    when installing the timing chain back, did you turn the timing gear all the way clockwise and install the chain?
    I notice that the timing gear does not lock in this car.
     
  17. donzoh1

    donzoh1 Active Member

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    Been awhile but I believe I followed steps outlines on this site to get timing chain/cover back on. I seem to remember installing the tensioner and then after the cover was in place, reaching down with a screwdriver to move a tab which releases the spring/ratchet. I always gently turn the motor thru a couple times by hand with no spark plugs in just to be sure there is no valve interference and that the cam and crank timing marks return together to their alignment positions.
     
  18. Mendel Leisk

    Mendel Leisk Senior Member

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    Repair Manual says to rotate the crankshaft counterclockwise a bit, to release the tensioner.