Red Triangle of Death

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by wbtannery, Jul 18, 2026 at 8:00 PM.

  1. wbtannery

    wbtannery New Member

    Joined:
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    Location:
    Atlanta
    Vehicle:
    2008 Prius
    Model:
    Base
    Hey there, I've got a trusty 2008 base model. I've put a lot of time and energy into keeping this thing chugging! This is the rough chronology of parts that I've replaced or cleaned over the last several years. I'll conclude by listing the current problems, and asking for thoughts!
    1. 2022
      1. replaced MAF sensor
    2. 2024
      1. replaced hybrid battery
      2. replaced spark plugs
      3. replaced water pump
    3. 2026
      1. replaced PCV valve
      2. replaced 12v battery
      3. cleaned MAF sensor
      4. cleaned throttle body
      5. replaced ignition coils
    so the issue that i've been dealing with for the last year or so has been intermittent engine knocking, that's slowly gotten worse. I've been burning oil, fuel economy has dropped considerably, and I've started to lose acceleration, especially moving uphill. Today, I got the Red Triangle of Death and a warning about my coolant levels. It really looks to me like the coolant reservoir is low or empty, so I imagine I'll need to find a way to get coolant into it without actually driving it to the auto parts store.

    I've yet to do a compression test, examine the oil myself to see if it's cloudy from coolant, or examine the cylinder heads to see if they've been sprayed clean by pressurized coolant. Pending that information, are there any reasonable guesses that could be made here about a diagnosis?
     
    #1 wbtannery, Jul 18, 2026 at 8:00 PM
  2. JC91006

    JC91006 Senior Member

    Joined:
    Nov 10, 2013
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    Location:
    Los Angeles, CA
    Vehicle:
    2008 Prius
    Model:
    II
    you should make sure there is coolant in the RADIATOR, not so important in the RESERVOIR. The radiator cap is under the front engine cover, that must be removed to access it. When the car is cooled, you can open the cap and check if the coolant is full.

    The thing I didn't see on your list of replacement parts is the inverter coolant pump. That is a common failure on this car and can cause the red triangle to come on. A good symptom this has failed is your AC system will not blow cold air when the car is hot.
     
    #2 JC91006, Jul 19, 2026 at 10:19 AM
    Brian1954 likes this.
  3. Tombukt2

    Tombukt2 Senior Member

    Joined:
    Nov 29, 2020
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    Location:
    Durham NC
    Vehicle:
    2009 Prius
    Model:
    Base
    If you still have the plastic cover over radiator cap use you're multi tool to remove the plastic curve over the cap . Now it removes easily forever on side of road. When the radiator cap is removed if you don't see fluid standing proud at the top of the neck you have a problem and you need to find out why quickly.
     
    #3 Tombukt2, Jul 19, 2026 at 11:05 AM
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