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2013 1.8l Prius cylinder head gasket replacement

Discussion in 'Gen 3 Prius Technical Discussion' started by donzoh1, Jan 19, 2019.

  1. Mendel Leisk

    Mendel Leisk Senior Member

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    Could it be the MAP sensor connector??

    Ah maybe not, that looks to be 3 wire:

    upload_2019-3-19_11-55-26.png

    Knock sensor wire?

    upload_2019-3-19_11-59-1.png
     

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    #81 Mendel Leisk, Mar 19, 2019
    Last edited: Mar 19, 2019
  2. donzoh1

    donzoh1 Active Member

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    Thanks for the ideas. It did turn out to be the knock sensor and I found one Google image that showed the black and white wire so I soldered them onto the correct pins.
     
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  3. FnRedPrius

    FnRedPrius Active Member

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    It you can get a couple of good pics, I can see if it matches the ones on my Gen4 harness. It should as I didn't change any sensors on my swap and everything fit.
     
    #83 FnRedPrius, Mar 20, 2019
    Last edited: Mar 20, 2019
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  4. donzoh1

    donzoh1 Active Member

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    I was able to find a Google image of the knock sensor and connect the wires again.
     
  5. mjoo

    mjoo Senior Member

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    It seems to me that cylinder 1 was the hottest since it was the only piston that expanded enough to polish the walls and because there's fewer carbon deposits. This makes sense since the EGR channel to cylinder 1 is the longest while the channels to cylinders 2,3,4 get progressively shorter in the gen 3. A longer channel would have slower EGR air flow and be easier to clog with EGR soot and oil. Eventually more deposits accrue in cyl 1 EGR channel vs. cyl 4 EGR channel.

    As the EGR flow becomes unbalanced it would cause more EGR to flow into cylinder 4 than cylinder 1. This would cause cylinder 1 to run leaner and hotter while cylinder 4 runs richer and cooler. A richer/cooler cylinder generates more soot in the combustion process (cylinder 4). More soot leads to faster depositing in the EGR system and the EGR merry-go-round accelerates.

    What's interesting is that the hotter cylinder 1 was not the cylinder leaking with antifreeze.

    The Gen 4 manifold has EGR channels that resemble a tree to help prevent the EGR flow from becoming unbalanced. This is to realize equal lengths (restrictions) across all EGR channels.
     
  6. Mendel Leisk

    Mendel Leisk Senior Member

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    I think the gen 3 manifold revision (maybe standard from 2012 model year on) also does that tree thing. Also, seems like gen EGR passages have much greater "amplitude", diameters close to double.
     
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  7. mjoo

    mjoo Senior Member

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    Do you have the part #?

    Pixel XL ?
     
  8. Mendel Leisk

    Mendel Leisk Senior Member

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  9. Mendel Leisk

    Mendel Leisk Senior Member

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  10. mjoo

    mjoo Senior Member

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    #90 mjoo, Mar 20, 2019
    Last edited: Mar 20, 2019
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  11. mjoo

    mjoo Senior Member

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    My take-away from this thread is engines with old-style intake manifolds may need more periodic EGR circuit cleanses than the popular 100k advice. The intake manifold may need shorter cleaning intervals than the EGR cooler to prevent the unbalancing of EGR flow and ensuing head gasket leak.
     
  12. Raytheeagle

    Raytheeagle Senior Member

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    I’m sticking to 50k miles and pair it with the engine coolant swap;).
     
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  13. The Critic

    The Critic Resident Critic

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    Sorry for the late response, I kept forgetting to reply. You are correct, I forgot you did a leakdown test and heard air hissing from the piston rings. Plus you have already had the head inspected and it passed. If that is the case, the air hissing from the piston rings (esp from cyl 4 )would explain the reduced compression. I am not sure what happened, but perhaps when the head gasket blew - the engine overheated and the rings got cooked? Or perhaps this engine is simply worn out?

    Considering how much time you've spent on this already, you may be better off doing the Gen4 engine swap. I think your only option at this point is to either rebuild the bottom end or start with a different short block (preferably from a 2015 or from a Gen4).
     
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  14. mjoo

    mjoo Senior Member

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    Is he still leaking coolant? Otherwise a couple of long piston soaks could be a more appropriate next move?
     
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  15. The Critic

    The Critic Resident Critic

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    I guess it depends on what his timeline is. If the piston rings are worn and causing a loss of compression, then soaking is unlikely to provide any significant improvement.
     
  16. mjoo

    mjoo Senior Member

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    Do you really think the piston rings are worn at 127k on a hybrid with probably 80k actual engine miles?

    Pixel XL ?
     
  17. The Critic

    The Critic Resident Critic

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    We do not know the operating conditions. If the car was used strictly on the highway then the engine could have been in-use for the entire time.

    The rings (or even the entire bottom end) could be worn for a number of reasons. At least to me, the goal at this point should be to find the most efficient, reliable and cost-effective (depending on your definition) way of getting this car back into service. In my opinion, that would be either a Gen 4 swap or even a new short block from Toyota. For me, downtime is a huge concern so I may view things a bit differently than others...
     
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  18. donzoh1

    donzoh1 Active Member

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    As of today, the Prius lives. It fired right up, having a little timing chain slap or something but then quieted fairly quickly. But, it has codes $03, $07, and $0A...current, pending, and permanent. The cooling system dropped from 15 psi to 10 psi over 12 hours with only air in it. I think this indicates a good head gasket seal.

    On 2nd teardown, the intake manifold and throttle body had a coating of oil or oil/coolant mix and I wasn't sure what to make of that. And, before I did anything at all to the car, it had code P0301 i believe which indicated cylinder 1 misfire. The original symptom was occasional rough running on morning startups. It was also losing coolant I think this might have been accumulating in cylinder 1 during engine cooling, due to a head gasket failure.
     
  19. donzoh1

    donzoh1 Active Member

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    Interesting Gen 4 swap idea. Is that pretty much a direct swap or do I need to worry about a bunch of ECU stuff and new sensor connections?
     
  20. cnc97

    cnc97 Senior Member

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    There are two sensors that the leads need extended. And the lower hose needs reworked. Or use the Gen 3 head on the Gen 4 block and it’s plug and play.