Coolant issue. Desperately need help. Update: Blown head gasket

Discussion in 'Gen 4 Prius Care, Maintenance and Troubleshooting' started by Donnie K, Jan 22, 2025.

  1. Donnie K

    Donnie K New Member

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    Hi yall, I’ll try to make this short. 2016 Prius 2 Eco. Please read through !

    In december, I noticed my coolant levels dropping. No visible leak that I noticed, but had to refill maybe once a week, so I kept topping off for about 2 weeks.
    Then, my check engine and coolant overheating light came on. I brought it to mechanic, who said I have cracked radiator. Charged me $1100 for it.

    I picked it up later that same day, and when I got in car, check engine light and overheating was still on. Also, I checked my coolant levels, and they were completely empty.
    Brought it back to mechanic the next day, who had absolutely zero answer as to why coolant was empty considering there was no leak and they should have refilled it after radiator fix.
    Mechanic said now I have a blown head gasket. (Despite saying there wasn’t a blown head gasket the day prior)
    And then while idling it later while wanting to put in blue devil (didn’t put any in) he came back and said thermostat is stuck in closed.

    Things to note: 1) my heater stopped working just before my car had first overheated. Mechanic fixed the radiator, and the heater is still not working.
    2) my car sat after head gasket diagnosis for 2 weeks. I checked coolant levels this time, completely full despite sitting for so long… which makes it more confusing why there was none when I checked.
    3) I had a bit of coolant residue on my engine by my coolant reservoir, unsure if this is from me spilling coolant while refilling or something else. I do have photos if needed.

    my mechanic has been lying to me so I lost his trust.
    Could this be something besides blown head gasket? Maybe water pump and/or thermostat, or heat exchanger?

    I really need help!!
     
    #1 Donnie K, Jan 22, 2025
  2. jdenenberg

    jdenenberg EE Professor

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    The heat exchanger in the catalytic converter of Gen 4 Prii tends to develop a coolant leak, This is a known issue and there is a TSB about it, Over heating the engine due to low coolant can destroy it so one has to detect the coolant loss before overheating occurs.

    The leaking heat exchanger can be replaced under warranty if it is still covered, but part availability is an issue. The heat exchanger can be bypassed easily as an unofficial repair.

    JeffD
     
    #2 jdenenberg, Jan 23, 2025
    Mendel Leisk likes this.
  3. BiomedO1

    BiomedO1 Senior Member

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    It's a known common issue predominantly with 2016-2017 model years. Unfortunately, your 'mechanic' is dishonest and trying to milk you of your hard earned cash. I would question if he replaced the radiator at all. Did he give you the defective part or even touch the car after you left? Why wasn't the thermostat replaced with the radiator? That's common practice, to avoid unhappy customer returning - but he wanted you back so he could fleece you some more....

    TSB: Coolant leakage at front exhaust pipe (Prius & Prius Prime) | PriusChat

    Good Luck........

    if it was the water pump or thermostat, you would find a coolant leak under your car. You seem to have not noticed anything since your mechanic told you had a radiator leak - again you should have a coolant puddle under your car - if it's leaking. Get it properly diagnosed rather than just firing a parts cannon at the car!!
     
    #3 BiomedO1, Jan 23, 2025
    Last edited: Jan 23, 2025
  4. Brian1954

    Brian1954 Senior Member

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    How many miles on the car?

    My guess is a failing engine water pump. You should get an OBD2 Bluetooth dongle and an app to monitor the engine coolant temperature.
     
    #4 Brian1954, Jan 23, 2025
    Last edited: Jan 23, 2025
  5. Mendel Leisk

    Mendel Leisk Senior Member

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    Time to ditch this guy. You're damn lucky you stopped him before he poured stop-leak product in.
     
    #5 Mendel Leisk, Jan 24, 2025
  6. rjparker

    rjparker Tu Humilde Sirviente

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    I would bypass the exhaust heat exchanger as a diagnostic step. If it stops the coolant loss either leave it bypassed or get on the list to have heat exchanger fixed.

    Top of engine bypass using existing temp sensor fitting and no hose
     
    #6 rjparker, Jan 24, 2025
  7. bisco

    bisco cookie crumbler

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    See the gen 4 stickies for the TSB
     
    #7 bisco, Jan 25, 2025
  8. Donnie K

    Donnie K New Member

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    Hi yall, I posted a post about my 2016 prius 2 about a week ago, thank you guys for responding.
    I have since brought it back to another mechanic, who said they used a camera and saw coolant in my cylinders. However, doesn’t really see coolant mixed with my oil.

    He also said he sees coolant pooled in the exhaust.

    Says I have a blown head gasket and I have to replace the heat exhaust exchanger.

    Is there any chance I don’t have blown head gasket, and only the exchanger? What are all the ways coolant can get into the cylinders?
     
    #8 Donnie K, Jan 29, 2025 at 6:35 PM
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