Thermostat (3rd gen) answers !

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Ben Schneider, Mar 7, 2019.

  1. AmazingFacts

    AmazingFacts Junior Member

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    One thing I noticed is that before the water pump/thermostat replacement, temperature stayed normal(180-190 ish) during light driving, but when throttle was pushed say around 60-75%, temp tended to spike to 200 ish, depending on throttle position. This tells me that it's important to monitor the temp often, whether you have a OBD live data or Scangauge etc. to prevent premature headgasket failures. OBD live readers are quite cheap these days, around $20-$35 at Amazon. I would recommend everyone to get one, but please do be careful as the OBD readers have very small font so can be dangerous to monitor while driving.
     
  2. AmazingFacts

    AmazingFacts Junior Member

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    250k miles.
     
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  3. AmazingFacts

    AmazingFacts Junior Member

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    It has 250k miles. I just bought it from the original owners in nearly new condition with only 1 small ding, perfect paint/interior, oil change/maintenace records every 5k miles from dealer, and very clean engine area EGR pipe from the outside seems almost new and replaced. My previous Toyotas went 400k, 300k without engine/tranny rebuilds, so I thought why not. I'm ready to replace hybrid battery cells and do a headgasket job when needed though.
     
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  4. AmazingFacts

    AmazingFacts Junior Member

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    Oh and yes thanks for the EGR link Mendel.
     
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  5. Mendel Leisk

    Mendel Leisk Sand Pounder

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    250k is well past the typical EGR sell-by date; either it’s charmed, or previous owners were on it. Yeah check the EGR pipe at least, ASAP.
     
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  6. AmazingFacts

    AmazingFacts Junior Member

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    Yes, I'm hoping previous owners were on the maintenance or replaced it. I'll report back what I find after it's unbolted.
     
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  7. ChapmanF

    ChapmanF Senior Member

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    One way to start is by getting the current overall EGR flow test result from the ECM (easy), followed by taking out the intake manifold and checking/cleaning its small EGR ports and gallery (almost as easy, much easier than the stem-to-stern EGR exercise).

    The manifold check/clean will give you confidence about what the overall flow test can't tell you (because it can't see differences at the four individual ports), and then based on what you've seen you can gauge the urgency of doing the rest.
     
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  8. AmazingFacts

    AmazingFacts Junior Member

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    Great perfect, thanks Chapman. This will certainly same me time. I'll report back my findings.
     
  9. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Checking the condition of this pipe:

    142552F0-73D3-489A-AA08-19BE9AC85716.jpeg

    is the easiest to get to. Good for getting your feet wet.

    Video #16 here:

    Nutz About Bolts Prius Maintenance Videos | PriusChat

    And it covers the removal needed for intake manifold access as well.

    A prep work step (for removal of the EGR cooler/valve assembly) would be to remove the nut on the stud on the underside of EGR cooler bracket. Sooner or later you need to do that, and with the nut removed it's not in any way destabilized, so just remove it and leave it off. It's a pain to access, best to get it out of the way at the outside, rather than be hung up on it later.

    If you have an E8 torx socket and are ambitious, remove that stud as well. I did this not too long ago, and found it very tough to turn. You don't want to strip the head so go slow and careful. With the stud off I THINK it makes EGR cooler removal easier; you then maybe DON'T have to remove the rear studs, between cooler and exhaust manifold. You still have to remove the front/top stud holding the cooler, but that one's easy to access.
     
    #29 Mendel Leisk, Aug 25, 2021
    Last edited: Aug 25, 2021
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  10. ChapmanF

    ChapmanF Senior Member

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    It seemed to me the studs on the rear were easier to take out—access is better—and with them out there wasn't any need to fuss with the stud in the evil bottom location. I just scooted the cooler off it sideways. It also made a convenient locating peg when I was putting the cooler back in position.

    As a bonus, if any damage happens taking those rear studs out, that's only the EGR cooler. Any damage taking out the evil bottom stud is to the cylinder head.
     
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  11. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Mines out, and staying out. :)
     
  12. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Just musing: at those stud-plus-nut locations you could sub a bolt, of appropriate diameter/thread/length. With a washer behind the head, since it’s the driven component. Make for easier removal. Especially with the bottom-of-cooler nut/stud combo just ditched.
     
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