What's on the back of engine, above oil pan? (Wet!)

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by MrPete, Jul 19, 2025 at 1:07 PM.

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  1. NutzAboutBolts

    NutzAboutBolts Senior Member

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    @MrPete

    Is your engine from a 4th gen engine? I see the black bolt in the back by the oil pressure sensor.
     

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  2. MrPete

    MrPete Active Member

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    Good questions...

    I use Techstream for intense stuff, and keep an OBDlink LX installed while on the road, etc.

    OBDlink does seem somewhat smart, yet I don't get the impression it's doing anything all THAT fancy. IIRC its mostly a question of which lines it knows how to communicate with.
     
  3. MrPete

    MrPete Active Member

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    It's a 2015 (final Gen 3 year) from Hybrid Pitstop. The first year they fully solved the piston/ring issues.

    But according to the diagrams even for 2011, there are some extra bolts on the back side.
     
  4. Iron Man Prius

    Iron Man Prius New Member

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    Final year for a Gen 3 block was 2017 for Prius V and CT200h..and the piston rings were technically changed February 2014, for the 14.5 cars. ;)
     
  5. MrPete

    MrPete Active Member

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    Right. But to install a 2016 engine in a Gen3 (normal) Prius is more than a little tricky.Two years in, I am appreciating the expertise and care of Hybrid Pitstop in their engine replacement/upgrade program. :)
     
  6. Mendel Leisk

    Mendel Leisk MMX GEN III

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    They solved it by finally acknowledging the low-friction piston rings they purposely spec'd, were an abysmal failure.

    Oh, and issued a TSB that says they'll replace pistons/rings on pre-revision Prius, IF it's burning more than a quart every 1100~1300 miles, AND has under 60k miles on the odometer.

    What a nice lot, always in our corner. :rolleyes:
     
  7. Iron Man Prius

    Iron Man Prius New Member

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    Not really if you put it together as plug and play for the Gen 3. JDM or Wrecking yard Gen 4, trying to adapt EGR and water lines..yes.
     
  8. rjparker

    rjparker Tu Humilde Sirviente

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    Recently they started offering a rebuilt gen4 engine for retrofit into a gen3 car. They install a gen3 head between the gen4 block and cam assembly so that the gen3 egr and water lines fit.

     
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  9. NutzAboutBolts

    NutzAboutBolts Senior Member

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    that’s pretty smart. Less modification on the coolant hoses and such. I wonder if the camshafts housing parts different from the gen4. If not, I bet reusing the gen3 head and egr is easier to plug and play.
     
  10. RightOnTime

    RightOnTime Senior Member

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    Yes, we started doing this about 5 years ago with Great success from our Test subjects that we trusted for honest feedback. The game changer was modifying the Felpro Headgasket to make it work effortlessly with the Gen 4 waterpump
     
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  11. rjparker

    rjparker Tu Humilde Sirviente

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    On my v it was the timing chain cover sealant. At first it just collected on the engine and the under cover. I changed the oil pressure switch and had a new tensioner and tensioner gasket installed with no results.

    Eventually it was cleaned up enough to capture the leak location:

    IMG_9003.jpeg

    After driving a while it was all over the oil pressure switch, that general area and some blew around that side of the engine.
     
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  12. johnHRP

    johnHRP Active Member

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    yeah.... Classic older style pre-2.5L engines timing cover. They almost always leak at the point where the head meet the cradle and timing cover. 3 surfaces rendezvous where oil allowed to passo_O.
    Mine leaking like that too since the standard waranty expired at 60k miles.
     
  13. Iron Man Prius

    Iron Man Prius New Member

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    Exactly what I mentioned, I think Pete was thinking FULL Gen 4 right out of the donor car, yes that's more tricky and moving parts.
     
  14. Iron Man Prius

    Iron Man Prius New Member

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    You wouldn't be able to have a plastic Gen 4 valve cover on a Gen 3 cam cradle. ;)
     
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