Pine Hollow Diagnostics does a Prius v Head Gasket

Discussion in 'Prius v Main Forum' started by rjparker, Nov 12, 2024.

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  1. rjparker

    rjparker Tu Humilde Sirviente

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    Clear narration and video with a a few new insights. Part 1

    Will a head gasket be enough?


     
    #1 rjparker, Nov 12, 2024
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  2. rjparker

    rjparker Tu Humilde Sirviente

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    Part 2
     
    #2 rjparker, Nov 13, 2024
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  3. rjparker

    rjparker Tu Humilde Sirviente

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    Is the oil filter the hardest part?
     
    #3 rjparker, Nov 14, 2024
  4. Mendel Leisk

    Mendel Leisk MMX GEN III

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    Yeah that was astounding. Some idiot put it on with an impact? Maybe been on for some time...

    He seemed to have one hell of a time breaking the bond between head and block.

    Don't really subscribe to his litany of likely causes, the "why it failed", but leave that for another day.
     
    #4 Mendel Leisk, Nov 14, 2024
  5. rjparker

    rjparker Tu Humilde Sirviente

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    He is just one of those Mechanical Engineers that thinks he knows something because he works on cars for a living.

    I think that car had a really advanced hg failure with coolant in the oil. Most likely the offbrand housing oring had swollen and seized.

    I think thermal cycling has validity and was apparently reinforced by Toyota Europe's inclusion of long idles and stop and go as hg failure contributors. I have seen 40 and 50f swings within minutes in idle and low speed driving tests while using ac where the fans don't shut off. Of course Pine Hollow was quoting Gasketmasters from a few years ago; they have migrated to more engine changes along with head gaskets.

    It would be good if PIne Hollow gives us a followup on his plain vanilla gen3 hg replacement down the road.
     
    #5 rjparker, Nov 14, 2024
    Last edited: Nov 14, 2024
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  6. Mr.Vanvandenburg

    Mr.Vanvandenburg Senior Member

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    Doesn’t this engine use stretch head bolts?
     
    #6 Mr.Vanvandenburg, Nov 15, 2024
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  7. rjparker

    rjparker Tu Humilde Sirviente

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    Toyota has an acceptable measurement for head bolt length and diameter. They also want timing chains measured as well as dimension inspections of many other timing and valvetrain parts.

    That is why I called this and most head gasket jobs plain vanilla.
     
    #7 rjparker, Nov 15, 2024
  8. Mr.Vanvandenburg

    Mr.Vanvandenburg Senior Member

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    There should be angle turns after the head bolts are torqued, as the bolts are stretch I looked it up. I did two 90 deg turns on my hg job on a Toyota truck. That’s a lot of turning from already very tight, and sets the bolts into the elastic zone as I understand it.
    I didn’t see him do the angle turns but maybe missed it. Also you can’t just throw a gasket on a head, it has to be perfectly cleaned and measured for warping. Cleaned while maintaining flatness, not with abrasive pads to make shiny for the eyes.
     
    #8 Mr.Vanvandenburg, Nov 15, 2024
  9. Mendel Leisk

    Mendel Leisk MMX GEN III

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    With 3rd gen (and likely 2nd through 4th as well), after initial torque, it's 90 degrees, then 45.
     
    #9 Mendel Leisk, Nov 15, 2024
  10. rjparker

    rjparker Tu Humilde Sirviente

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    Second gen is 90 90 IMG_6728.png
     
    #10 rjparker, Nov 15, 2024
    Last edited: Nov 15, 2024
  11. Mendel Leisk

    Mendel Leisk MMX GEN III

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    Where’s that from? My 2010 Prius repair manual says 90, then 45. IIRC several YouTubers say sim.

    IMG_6009.png
    Also initial torque is 36 lb/ft.
     
    #11 Mendel Leisk, Nov 15, 2024
  12. Mendel Leisk

    Mendel Leisk MMX GEN III

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    Ah lightbulb goes on; you’re clarifying, second Gen is 90, then another 90. (y)
     
    #12 Mendel Leisk, Nov 16, 2024
  13. Mr.Vanvandenburg

    Mr.Vanvandenburg Senior Member

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    The 180 degrees is only about .030”. I was looking by eye at my old versus new head bolts and it isn’t very length difference much by eye side by side, head to toe. By eye the old are ok maybe, but not really. Anyway don’t know if this guy did the torque to yield.
     
    #13 Mr.Vanvandenburg, Nov 16, 2024
  14. Mendel Leisk

    Mendel Leisk MMX GEN III

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    Further, from my gen 2 pdf:

    upload_2024-11-16_11-52-9.png
    Again, gen 3 is 90, then 45.
     
    #14 Mendel Leisk, Nov 16, 2024
  15. Air_Boss

    Air_Boss Senior Member

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    What’s the point of a set torque value when additional turns are required?

    Like the old saw, torque until bolts strip out, then back off half a turn…
     
    #15 Air_Boss, Nov 17, 2024
  16. rjparker

    rjparker Tu Humilde Sirviente

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    They want it tight using special bolts which do not have to be retorqued after initial warmup. This is to ensure the head gasket does not leak during thermal expansion and contraction. Does not always work.
     
    #16 rjparker, Nov 17, 2024
    Last edited: Nov 17, 2024
  17. Air_Boss

    Air_Boss Senior Member

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    I get that. In my experience, the desired degree of ‘tightness’ is specified via a set torque value and re-torqued to set after X hours.
     
    #17 Air_Boss, Nov 17, 2024
  18. Mendel Leisk

    Mendel Leisk MMX GEN III

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    Considering the bolts are oiled, that initial torque should tension them fairly uniformly?
     
    #18 Mendel Leisk, Nov 17, 2024
  19. rjparker

    rjparker Tu Humilde Sirviente

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    Most conservative mechanics would replace the head bolts but a head bolt can return close enough to its original length to be reused. So Toyota has a spec on the maximum length increase and the minimum thread diameter.

    IMG_6738.jpeg IMG_6739.jpeg
     
    #19 rjparker, Nov 17, 2024
  20. Mr.Vanvandenburg

    Mr.Vanvandenburg Senior Member

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    I followed all that when I did the gasket, not wanting to have to redo the job. I just used new bolts. I did take measurements with a micrometer of the diameters, calipers for length, but nothing stood out as I can reuse the bolts. The stretch is only 3/4 mm or about .030”, so new bolts are the sure bet. This number is from the thread pitch of 1.5 mm.
    Someone asked why not only torque. This is why and the head gasket is designed for stretch bolts, not just torque.

    https://www.rockauto.com/info/604/24_EN.pdf
     
    #20 Mr.Vanvandenburg, Nov 17, 2024
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