My son drove his Prius into 2+ feet of standing water

Discussion in 'Gen 3 Prius Technical Discussion' started by GasSavings, Dec 30, 2025 at 7:10 PM.

  1. GasSavings

    GasSavings Junior Member

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    My son’s a new driver, just got his G licence, and loves his Prius. He’s blaming his nav or failing to respond correctly for driving through deep standing water getting off the Highway, vs pulling onto the shoulder. Be that as it may, he drove through this deep water (top of hood) that, after him, stranded a Ford F-150 and several other cars. At least he made it through the water bog!

    He managed to drive another 1.25KM, almost home, and “the car started shutting down in stages”, first the stereo, then the dash, then the whole car shut down.

    He managed to park it safely and called me at 11:30pm for help. The car seemed dead (12V) so we used a jumper pack and got it to try and start many times. Sounded like a really rough, misfiring rattling (heat shields) mess. We boosted from under the hood, (fuse box terminal) and at back of car.

    We took out the air filter and it was (really) water-logged. :-/

    No luck so we flatbedded it home (only 1KM!) and it sat in the driveway at -12 degrees Celsius 10.4 F and frozen. We finally installed the new AGM battery we bought 2 years ago, after fully charging it over night.

    Got a Green Ready Light (!) and was hopefull but one clunk sound (to me it seemed frozen or seized and then flashing green ready light and nothing. The flashing green ready has been the common theme here!

    Pushed car into garage with space heaters and model y set to 21 and “camp mode” and got temps up to 10 degrees or 50 F.

    Tried to start again after 26 hours, and got a rattlingly quick misfire then flashing ready light.

    Pulled the plugs before the start event thinking we’d blow the water out of cylinders but no such luck.

    Drained the oil and replaced with heated oil at 113 F thinking it couldn’t hurt to try but it didn’t help. There was a foamy film on the drained oil, but not a lot.

    Marked crankshaft pulley with sharpie, put a 19mm socket on an 18” breaker bar, and couldnt’t turn over the crankshaft even with the plugs out. Can the MG1 jamb the engine trying to start? Maybe engine is still frozen? I don’t know what to do other than give it more time to thaw out?

    other than the non-ready light, lots of clicking from HV battery area.

    The car is in excellent shape and only has 51k miles on it. We both really like the car and are afraid Toyota will write off the car and write us a cheque which we don’t want. He said he’d like to drive it another 10 years, and I don’t blame him. This little car has something about it we love, we don’t want to give up on it, can’t afford to replace it, but can put money into a repair if needed, but we’re just puzzled as to what’s going on.

    Lastly we tried Maintenance Mode. Tried to start for maybe .25 second and that was that. Nothing.

    Would really appreciate some real world feedback from anyone that has been through this and not just ChatGTP because that hasn’t helped us much.

    Thanks so much!

    P.S. I hope I’m in the right forum, sorry if I missed that
     

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    #1 GasSavings, Dec 30, 2025 at 7:10 PM
    Last edited: Dec 30, 2025 at 7:57 PM
  2. ASRDogman

    ASRDogman Senior Member

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    May it rest in peace......
    Very likely you bent at least 1 rod because water was in the cylinders, and also the engine.
    At the very least, you probably need a new engine.
    But with all the water everywhere, eventually you have more electrical issue from corrosion....
     
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  3. frodoz737

    frodoz737 Top Wrench

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    Your Insurance Co. will likely total it.
     
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  4. BiomedO1

    BiomedO1 Senior Member

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    Yep; most likely hydro-locked, bent and/or broke something.
    You need to replace the engine - water does NOT compress like air.
     
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  5. bisco

    bisco cookie crumbler

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    i think the service manual might cover flooded prius
     
  6. GasSavings

    GasSavings Junior Member

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    I came here looking for troubleshooting techniques not sarcasm but I haven’t received much yet. Let’s see what tomorrow or the next day brings. In the meantime it’s thawing in the garage.
     
  7. ASRDogman

    ASRDogman Senior Member

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    :eek::eek::confused::confused:(n)(n)

    If you wanted someone to hold your hand and tell you all is okay and 10 hail dead woman's will make
    it all okay, you've certainly come place to the wrong place.

    Everyone is trying to tell you like it is, from experience.

    There are things that could be said about the incident, but I think we try to be nice....
     
  8. VelvetFoot

    VelvetFoot Active Member

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    My owners manual actually has something on flooding. I don't think very helpful though. This is for a GEN five.
     
  9. frodoz737

    frodoz737 Top Wrench

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    Have it towed to the Dealership and get it checked out. You might get lucky.
     
  10. BiomedO1

    BiomedO1 Senior Member

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    If can't turn the crank shaft, how do you expect Mig1 to crank the engine?
     
  11. GasSavings

    GasSavings Junior Member

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    Not at all, just looking for something else a DIYer can try before taking it to a mechanic.
     
  12. ChapmanF

    ChapmanF Senior Member

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    There is a technical service bulletin you should read that is referenced in this post:

    https://priuschat.com/posts/2414814

    You'll notice that the strictest recommendations it makes apply for salt water. The news can be a little bit better if the water was fresh.
     
  13. VelvetFoot

    VelvetFoot Active Member

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    MC-10133654-9999.pdf
     
  14. Hayslayer

    Hayslayer Active Member

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    The reality is the car is now effectively junkyard material.

    Driving a car (engine running) through 2 feet of water, when the air intake is only 1 foot above the ground is an engine slayer. The engine effectively acted like a shopvac/wetvac and sucked water straight up the air intake ductwork into the engine until it locked down, which was probably pretty quick and catastrophic. At a minimum, you now have bent connecting rods. The car continued driving only due to battery power. The engine was already toast. Then, anything that had water in it (ie engine, transaxle, etc) was turned into an ice cube and likely damaged more components.

    By the time you deal with the drivetrain problems, corrosion issues are already going to start forming on any electrical plug that found itself submerged, turning the car into a future money pit of problems. If you want to throw money at it, take it to a dealer and let them examine it. They'll provide you with a list of everything that needs replacing/cleaning and hand you a bill for $500 for the time took to inspect. Unless they're nice enough to just tell you straight out of the gate that the car is done.
     
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  15. VelvetFoot

    VelvetFoot Active Member

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    I’ve read articles about battery fires after flooding, so there’s that too. That bulletin says to park it away from valuable stuff, lol.
     
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  16. frodoz737

    frodoz737 Top Wrench

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    The additional problems with a Prius are all the electronics. As I respectfully stated earlier, the Insurance Co will likely just total the vehicle. They have a lot of experience with this kind of damage.
     
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  17. Mendel Leisk

    Mendel Leisk MMX GEN III

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    Toyota's got nothing to do with this. How's your insurance, what kind of coverage?
     
    #17 Mendel Leisk, Dec 31, 2025 at 12:26 PM
    Last edited: Dec 31, 2025 at 12:33 PM
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  18. GasSavings

    GasSavings Junior Member

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    I haven’t contacted them yet but I’m hoping it’s converted under compressive coverage and there is a $1000 deductible.

    a replacement car is C$10-13k with similar mileage.

    thank you for your reply.
     
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  19. GasSavings

    GasSavings Junior Member

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    Most likely, thank you.
     
  20. GasSavings

    GasSavings Junior Member

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    thank you, I appreciate your thoughts and the advice.