Cam shaft and Crank Shaft Notches not lining up - 2012 Prius

Discussion in 'Gen 3 Prius Technical Discussion' started by JLotta, Nov 28, 2025 at 12:27 AM.

  1. JLotta

    JLotta New Member

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    Hi all!
    My husband is repairing the head gasket on my sons 2012 Prius. He did this same repair on my 2010 Prius.
    When he put the timing chain on my 2010 Prius, the Cam shaft and crank shaft notches all lined up perfectly. This time, they are not lining up. Is it normal for them to not be lined up? Was it coincidence that they were lined up when he did my Prius?

    Also, does the 2012 Prius use a "hunting" timing system? (we've read about this).

    My husband doesn't know if he should manually adjust the cam and crank shaft so they line up, or something else?

    Any experiences and solutions would be greatly appreciated. He has to have this repair done by Saturday :(
     
    #1 JLotta, Nov 28, 2025 at 12:27 AM
  2. PriusCamper

    PriusCamper Senior Member

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    Please let us know an exact distance/measure/photo for: "they are not lining up"

    How much work was done on the head before it was put back together?
     
    #2 PriusCamper, Nov 28, 2025 at 1:45 AM
  3. JLotta

    JLotta New Member

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    Hey there! I'll have him get a photo and reply to this. Thanks for your help.
    While I'm waiting on that, could you tell me if it's true that Prius' have a "hunting" timing system? In other words:

    "The timing marks on the camshaft and crankshaft sprockets are intentionally designed to be slightly "off" relative to the number of teeth or chain links. This design ensures that the same tooth on a gear does not contact the same link of the timing chain or same cogs of the timing belt during every single rotation.
    This maximizes the least common multiple (LCM) of rotations required for a specific gear tooth and chain link to align again. This distribution of contact points prevents premature wear and tear on a single point, thereby extending the overall life and durability of the timing chain and sprockets. "

    Is this the kind of timing system a 2012 Prius 3rd generation has?
     
    #3 JLotta, Nov 28, 2025 at 7:48 AM
  4. ASRDogman

    ASRDogman Senior Member

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    The timing chain is the same for all Gen 3 Prius'.
    He will have to manually set the crank to TDC, and align the cams to the correct
    location, then install chain aligning the gold color links...

     
    #4 ASRDogman, Nov 28, 2025 at 7:58 AM
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  5. ASRDogman

    ASRDogman Senior Member

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    That is not true. There is no floating. There is variable valve timing.
    The initial timing marks must be set correctly. After that, it's automatic.

    After setting the chain, and releasing the chain tensioner, if you rotate the crank 720 degrees,
    two full turns, the timing marks should line up. The colored links won't, unless you keep rotating the
    crank about 30 times, at least that's what was posted on here.

     
    #5 ASRDogman, Nov 28, 2025 at 9:30 AM
  6. ChapmanF

    ChapmanF Senior Member

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    On a gen 3 Prius, it's 35 cam revolutions, which is 70 crank revolutions; that's been posted on here several times.

    The description given in post #3 of a 'hunting' system (interesting term, hadn't heard that one before) simply refers to the math that is behind those numbers, covered in older posts here and here.

    As explained there, the choices Toyota made did not "maximiz[e] the least common multiple"—if they had made the chain two rollers longer, you would need 142 crank revolutions to line the marks up again!
     
    #6 ChapmanF, Nov 28, 2025 at 2:12 PM
    Last edited: Nov 28, 2025 at 2:19 PM
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