Signs that a 3-way coolant control valve is failing?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by pasadena_commut, Sep 25, 2019.

  1. pasadena_commut

    pasadena_commut Senior Member

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    What signs would indicate that a 3-way coolant control valve is failing?

    When the Dorman inverter pump failed this weekend I heard a sound which dolj identified as a 3-way coolant control valve on its way out (sound file attached). However, the car seems to be working normally, and under the same conditions as before the odd sound has not returned. Could just be that it is an intermittent failure at this point. This 2007 Prius does have 117K on it and it is probably the original valve. The heat works and does not make any odd noises. The thermos fills and empties as it should, or at least sounds like it is doing so, just as it has for the last 2K miles (as long as we have had the car). The thermos related sounds are pretty strange and a little uneven, maybe the valve is modulating it somehow? If somebody has a recording of the normal sounds the thermos makes when filling and emptying please post them. Thanks.
     

    Attached Files:

    #1 pasadena_commut, Sep 25, 2019
  2. dolj

    dolj Senior Member

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    From what you have written subsequent the that first post where you posted that sound file, it sounds like the valve may only be only intermittently having a problem. From what I understand, failure of that valve will only cause the preheating function to be inoperable or the loss of cabin heat. However, the ICE will operate without any adverse effect, indefinitely. Usually it is accompanied by the P1121 (and/or sometimes P1122) DTC.

    If it is functioning at this point, I wouldn't worry about it anymore until it makes the noise constantly with accompanying P1121.
     
    #2 dolj, Sep 26, 2019
  3. Aegean

    Aegean Active Member

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    My three way valve was sticking and I had the P1121 code for a few months. I was just using Techstream to reset it and after 3-4 weeks it was coming back. Finally, I found time and changed it. I did not notice any issues while the three way valve was giving the P1121 code and I was driving the car for several months. I would not worry much.
     
    #3 Aegean, Sep 26, 2019
  4. pasadena_commut

    pasadena_commut Senior Member

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    Does P1121 bring up the red triangle of death or just the CEL?
     
    #4 pasadena_commut, Sep 26, 2019
  5. dolj

    dolj Senior Member

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    The repair manual indicates only the MIL (Malfunction Indicator Light aka Check Engine Lamp (CEL)) is lit when a P1121 is set.
     
    #5 dolj, Sep 27, 2019
    m.wynn likes this.
  6. pasadena_commut

    pasadena_commut Senior Member

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    Thanks for the info.
     
    #6 pasadena_commut, Sep 27, 2019
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