Engine coolant inside catalytic converter

Discussion in 'Gen 4 Prius Technical Discussion' started by Megatron1337, Mar 4, 2019.

  1. Megatron1337

    Megatron1337 Junior Member

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    It's been a week that I noticed I was loosing coolant but couldn't see a leak. Brought it to the dealership and they found Coolant in the cat converter. They will be changing a few parts connected to my exhaust system including the cat converter to fix the issue. All under warranty. I have a 2016 gen4 with 78k km's. Has this happened to anyone or ever hear of this happening?
     
  2. alanclarkeau

    alanclarkeau Senior Member

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    Which Catalytic Converter? There are 2 (TWC in the diagram). Did they indicate how it was getting there?

    upload_2019-3-6_8-47-12.png

    Clutching at straws - maybe the Exhaust Heat Recirculation System ... BUT ...

    The odd thing is - the Exhaust Heat Recirculation System (on some USA and Canadian Models - maybe other cooler climes too) which has coolant circulated to it - is AFTER the TWC (Two Way Catalytic Converter).

    upload_2019-3-6_8-32-37.png
    upload_2019-3-6_8-33-34.png
    upload_2019-3-6_8-41-6.png
    upload_2019-3-6_8-35-2.png
    [Note that the white arrows indicate COOLANT, black arrows indicate EXHAUST GAS]

    upload_2019-3-6_8-34-13.png
    upload_2019-3-6_8-37-39.png

    No - I don't know, sorry. We don't have the Exhaust Heat Recirculation System here.
     
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  3. Megatron1337

    Megatron1337 Junior Member

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    I believe it's the second one you circled.
    It started last week when I was driving and the inside of my car was not heating up and it was blowing cold air. I checked the engine coolant level and it was empty. I suppose the check engine light didn't come on because the engine still had its engine being cooled by the coolant? but the coolant that's supposed to get recirculated wasn't getting looped back because exhaust heat recirculation system?


    At the 21ist minute you can see the system that's defective in my car. I believe it will all be replaced.
     
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  4. ekpolk

    ekpolk What could possibly...

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    I'm going to be watching this thread, primarily for my own edification, since I know little about this system, other than its mere existence. I understand it is, in effect, the "replacement" for the "Thermos" system which we had in the Gen-2 cars?

    That said (and asked), the first thing that comes to mind is how on earth any coolant, if it had leaked out from the liquid/coolant side of the heat exchanger, would "survive" as identifiable coolant for any appreciable time in any other part of the exhaust, pipes or especially the cat?!? I would think that it would either boil or burn off almost immediately, given the temperature levels involved. What am i missing (other than a few assorted loose screws...)?
     
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  5. Megatron1337

    Megatron1337 Junior Member

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    I wouldn't know, it's what they told me!
    FYI, it took them only 30 minutes to figure out what the issue was after I brought my car in. I told them about how I ended up checking for low coolant ( heater was blowing cold air and that I didn't see any leaks).With the symptoms I explained to them and the speed it took them to find the issue, leads me to believe they have seen this happen before. The mechanic came and talk to me, said they stuck a camera inside and saw the coolant. Perhaps the coolant wasn't in the cat , but inside the other part?
    Also FYI I brought the car at the dealership on Monday,told me that I can't leave with the car for obvious safety reasons. Told me the parts are B.O. for a few days and they will call me when they have the parts. They borrowed me a 2018 Prius V with 800 km's .
     
  6. alanclarkeau

    alanclarkeau Senior Member

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    Thanks - I knew about that video but couldn't spot it in a hurry (I was expecting visitors who've gone now).

    The engine coolant being empty won't always trigger the Check Engine Light. Though in modern computer monitored cars, I'd hope there was some way to get it to light.

    It's never happened to me, but my Dad twice warped the head on vehicles - both times, there had been a catastrophic loss of coolant (first time dealership didn't tighten a hose after service - and it stopped 7 minutes later when it blew off - 2nd time more routine). But the coolant disappeared so quickly that the temperature gauge never went high - as there was no coolant to heat it. The cars just stopped both times.

    Hope the repair is quick - good they've given you a loan car.
     
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  7. Dxta

    Dxta Senior Member

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    You maybe having a failed cylinder head gasket, or one of the loops of the cooling system is leaking into the exhaust system.
    In this case, I bet you should see white vapour from your exhaust tail pipe when the ICE runs.
     
  8. Megatron1337

    Megatron1337 Junior Member

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    Mechanic mentioned a defective backflow valve. Does that have anything to do with the loops of the cooling system? He smelled the engine coolant when he raised the car around the exhaust system.
     
  9. padroo

    padroo Senior Member

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    I'm thinking they have a TSB out on this leak.
     
  10. Megatron1337

    Megatron1337 Junior Member

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    That could explain the reason why they figured out the issue within 30 minutes of me bringing the car in. Do you have a link to The TSB ?
     
  11. CooCooCaChoo

    CooCooCaChoo Active Member

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    I have yet to see or hear of a TSB on this issue. You may have read it on here from other owners with the issue, as I remember a thread or two on it as well, but no recall.
     
  12. kithmo

    kithmo Couch Potato

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    The Cat is the box in front of the heat exchanger, the coolant will have leaked into the heat exchanger, vapourised then condensed further back in the exhaust, where they probably stuck the camera.
    It looks like the front exhaust is all one piece from the manifold, incorporating the cat, the heat exchanger and the central (sub) muffler, with a joint to the back half, which is separate.
     
  13. alanclarkeau

    alanclarkeau Senior Member

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    There's a ball-joint between the 2 Catalytic Converters - not sure if it separates? Though this diagram sort-of implies it might:
    upload_2019-3-6_23-20-48.png
     
  14. kithmo

    kithmo Couch Potato

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    Where is the 2nd cat, I can only see 1 ?
    There is a ball joint at the front of the exhaust, joining it to the manifold (not on the diagram) and a ball joint at the joint between the front half of the exhaust and the back half, both labelled "a*" in the diagram, there isn't a cat in front of the first joint (manifold) and there isn't a cat behind the second joint to the back half of the exhaust, only a big muffler at the back end.
     
  15. ekpolk

    ekpolk What could possibly...

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    Check out the more complete diagram in the #2 post in the thread. The first cat (TWC) is essentially immediately downstream of the confluence of the exhaust manifold; the second is maybe 12-16 inches further downstream, and appears just before the heat exchanger device.
     
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  16. FuelMiser

    FuelMiser Senior Member

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    Any idea how to tell which USA models? Probably a good idea to keep an eye on the engine coolant reservoir...
     
  17. ekpolk

    ekpolk What could possibly...

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    Awww, c'mon -- coolant hoses in close proximity to catalytic converters -- what could possibly go wrong. . .?
     
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  18. ekpolk

    ekpolk What could possibly...

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    Seriously though, I'm a bit perplexed at the suggestion I too have noticed that not all the cars have this "feature." If it's largely an emissions control measure, for quick engine heating to "clean running" temps, then I'd expect all cars to be so equipped, just like all the Gen-2 cars had the so-called Thermos, for just this same reason.

    EDIT: It's not as if people never move their homes from warmer climates to colder ones. If so, then what? You drive a "dirty," slow to warm-up Prius from then on???
     
  19. Megatron1337

    Megatron1337 Junior Member

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    If you check out the YouTube video I posted, starting at 17 minutes he explains the whole heat exchange recirculation components and he shows both catalytic converters. He talks about the first cat right at the beginning of the 17 minute mark roughly if I'm not mistaken.
     
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  20. kithmo

    kithmo Couch Potato

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    Same diagram ?
    It goes, manifold joint, oxygen sensor, cat, heat exchanger (not a cat), secondary muffler, ball joint, rear exhaust.
     
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