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Transaxle temperature limit

Discussion in 'Prius c Technical Discussion' started by Sonic_TH, Oct 20, 2022.

  1. Sonic_TH

    Sonic_TH Active Member

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    What is the temperature limit of the motor generator 1 and motor generator 2, before a code comes from these overheating?

    2 days ago on a long hill trip, going up and down, my 2012 Prius C motor generator 2 temperature got to 116° C, seems hot but i would like to know what is the maximum temperature these can take.
     
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  2. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    I understand the ATF to be the most temperature-limited thing in there, and that should be good up to about 125°C
     
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  3. Elektroingenieur

    Elektroingenieur Senior Member

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    In the Repair Manual series (more info), the malfunction thresholds for the “Drive Motor ‘A’ Temperature Sensor” (P0A2B, P0A2C, P0A2D, and P0A2E) and “Generator Temperature Sensor” (P0A37, P0A38, P0A39, and P0A3A) diagnostic trouble codes are either not mentioned at all or stated only as “TMC’s intellectual property,” that is, trade secrets of Toyota Motor Corporation.

    The Data List pages give the following “Normal Conditions”:

    Motor Temp No2 (MG1 temperature):
    While driving at an ambient temperature of 25 °C (77 °F):
    25 to 100 °C (77 to 212 °F)​
    Motor Temp No1 (MG2 temperature):
    While driving at an ambient temperature of 25 °C (77 °F):
    25 to 90 °C (77 to 194 °F)​

    I don’t know if temperatures above these limits are necessarily abnormal, however.
     
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  4. Sonic_TH

    Sonic_TH Active Member

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    If the ATF gets past 125° C what could happen to it?

    My Prius C has 126,000 miles, still the original ATF.
     
  5. Sonic_TH

    Sonic_TH Active Member

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    Well, i guess the flat wire stators can take higher temperatures, maybe that's why Toyota removed the coolant cooler from the transaxle.
     
  6. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    That's roughly the point where some permanent chemical changes will start to occur in many oils. The oil breaks down a little bit, can form some waste deposits aka sludge and lose some useful lubrication properties.

    A few hours per year at 116 isn't going to hurt anything.

    My own theory is that with the lighter weight of the Aqua model, they were able to simultaneously eliminate leak potential, reduce the amount of coolant required and trim the parts count a little. All good for cost savings and even further weight savings. Similar to the use of a single radiator fan where all the big Priuseses have two.
     
  7. Sonic_TH

    Sonic_TH Active Member

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    Well good thing that it was at those temperatures for a few minutes, when i arrived i turned the car off for a few hours.


    I see, makes sense, the Prius C being made to be cheaper to buy, but it has also proven to be more reliable, i have yet to see a failed transaxle in a Prius C.
     
  8. douglasjre

    douglasjre Senior Member

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    I've gotten MG1 and MG2 to higher temperatures and at some point the car goes into a 80% power mode to protect the system.
     
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  9. Sonic_TH

    Sonic_TH Active Member

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    Do any warning lights come on or something?
     
  10. priusCpilot

    priusCpilot Active Member

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    I remember a while ago that someone mentioned 325F is when the light comes on.
     
    #10 priusCpilot, Oct 25, 2022
    Last edited: Oct 25, 2022
  11. Sonic_TH

    Sonic_TH Active Member

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    The ''Check hybrid system, stop the vehicle in a safe place immediately'' one?
     
  12. priusCpilot

    priusCpilot Active Member

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    I don't remember but maybe some searching might show. I want to say that it was a temp warning with the red triangle.
     
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  13. rjparker

    rjparker Tu Humilde Sirviente

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    My experience with a v is mg temps are close to engine temps. 240f would be way too high in my case even though the stated limit is at 323f. In the v design there is an extra coolant loop from the inverter pump to the transaxle because of the v's higher load carrying capability. As a result transaxle temp can impact inverter temps which are alarmed at 149f. That loop goes to the inverter first, the transaxle and back to the radiator.

    IMG_0317.jpeg
     
  14. Sonic_TH

    Sonic_TH Active Member

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    Toyota should have added a separate small cooling system for the transaxle, the inverter is quite sensitive to temperature and using the same coolant from the inverter to cool the transaxle does not seems like a good idea for the lifespan of the inverter.
     
  15. rjparker

    rjparker Tu Humilde Sirviente

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    Actually the v’s transaxle coolant source could be the engine water pump. (Edit: It is the inverter water pump. See below)




    Recent 102f Ambient after Freeway Drive
    IMG_2425.jpeg
     
    #15 rjparker, Aug 24, 2023
    Last edited: Aug 24, 2023
  16. ChapmanF

    ChapmanF Senior Member

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    Nope, the engine has one cooling system, and the inverter and transaxle have the other one.

    v is a little bit different in having a second water jacket on the MG2 side. (Those passages are also present on the non-v Gen 3 liftback transaxles—it's the same aluminum case—but without the cover plate and hose nipples to close them off and make a usable water jacket.)

    [​IMG]
     
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