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Blocked Inverter Coolant Flow

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by sleeperbot, Sep 15, 2018.

  1. sleeperbot

    sleeperbot Junior Member

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    Hi all,

    Long time lurker; first time poster.

    I have a 2009 with over 200k miles that I've owned for two years. Learned a lot from these forums about replacing HV battery modules and balancing the pack. Have done that a few times.

    On a test drive after a recent replacement and balancing the car threw the Red Triangle after about 15 minutes of city driving and went into limp mode. After a stop at a light it would not move. After a brief rest it drive again as normal but went limp after about 8 minutes, close to home.

    Torque Pro shows all the HV blocks with good voltages. It read two DTCs:

    P0A78 & P0A94 (not sure how to pull sub codes)

    I suspect that the inverter or something is overheating as there is no flow visible in the reservoir. I assumed the pump was dead and replaced it. Still no flow. Seems both the old and new pumps work fine.

    So I drained the old coolant. Surprise. The inside of the drain plug was filled with sediment (like peanut butter.) A lot of visible sediment in the drain pan too. Filled up the system again and bled it but still no flow.

    I'm sure this sediment is all throughout the system and causing the block. How do I clean this out without damaging anything? What's causing this problems so I won't have to do it again? And will this fix my issues with the converter?

    Thanks for any help you can lend. WP_20180914_21_20_52_Pro.jpeg WP_20180914_21_14_00_Pro.jpeg

    Posted via the PriusChat mobile app.
     
    #1 sleeperbot, Sep 15, 2018
  2. sleeperbot

    sleeperbot Junior Member

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    Correction on this: my Prius is a 2006.

    Posted via the PriusChat mobile app.
     
    #2 sleeperbot, Sep 15, 2018
  3. Stimp

    Stimp Member

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    Sounds like silicate based coolant was mixed with SLLC. Maybe there are chemical flushes from the parts store that can clear it out...if not...

    Are the pump hoses clear? That's where I'd start, massage any sludge out if possible. You could disconnect the pump and fill the system with water and see where it comes out. Also could be blockage in the radiator. Compressed air would be useful to dislodge anything.

    Next step would be to remove the inverter and check passages in that if everything else is clear. One guy had a time lapse video of doing that recently here, but I'd try to avoid it.
     
    #3 Stimp, Sep 15, 2018
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  4. bisco

    bisco cookie crumbler

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    never seen anything like it before
     
    #4 bisco, Sep 15, 2018
  5. sleeperbot

    sleeperbot Junior Member

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    Kinda scary when someone with 70k post says they've never seen anything like it before ;}

    I'll try your suggestions Stimp to disconnect the pump and massage the hoses. How do you use the compressed air? (the opening is big but the nozzle is small.)
     
    #5 sleeperbot, Sep 15, 2018
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  6. edthefox5

    edthefox5 Senior Member

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    There's a system that's never been maintained.

    Going to be difficult to clean it all up because there's a huge cross section of pretty small aluminum cooling channels under the Inverter and then it goes through a standard radiator the bottom half of the engine rad is the Inverter coolant section and then it also goes though the transmission.

    The G2 is very hard on the inverter coolant and very easy on the engine coolant. Every time I see a post about someone replacing there engine coolant I think that's not the one you should be changing.

    I would check the rad first. Disconnect the in and out hoses and hook up a garden hose and see if that rad is clear. Inverter section will be very difficult to clean out I guarantee you the inverter cross section cooling channels are clogged. You may have to replace the inverter.
     
    #6 edthefox5, Sep 16, 2018
    Last edited: Sep 16, 2018
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  7. Stimp

    Stimp Member

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    Use air and water to loosen things up so you can get some kind of flow going, you'll have to be creative. Then it will have to be flushed with something like Radiator Flush | Coolant System Flush & Cleaner | BlueDevil a more concentrated organic acid than pink coolant. It might take some time and effort, but hopefully it will keep you from having to replace the inverter.
     
    #7 Stimp, Sep 16, 2018
  8. sleeperbot

    sleeperbot Junior Member

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    I had seen pictures of blocked channels in a link from another post in my research. I may indeed need to replace the inverter ed. Hopefully, the worst of it is in the radiator. Thanks for the product suggestion Stimp. This is going to be messy!
     
    #8 sleeperbot, Sep 16, 2018
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  9. bisco

    bisco cookie crumbler

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    salvage inverters are pretty cheap
     
    #9 bisco, Sep 16, 2018
  10. sleeperbot

    sleeperbot Junior Member

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    I noticed that too bisco. But I could not find a good video of anyone replacing the inverter for a Gen 2. I ordered a Haynes manual, but is there a good post or site that I could reference too?
     
    #10 sleeperbot, Sep 16, 2018
  11. bisco

    bisco cookie crumbler

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    #11 bisco, Sep 16, 2018
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  12. exstudent

    exstudent Senior Member

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    Get Techstream w/ mini VCI ($20-$30 Amazon) spare 32bit Window OS laptop, Mac install possible.

    Techstream is the official software made for Toyota/Lexus that the dealers use. This guarantees ability to read ALL codes, and do so much more the toy OBD2 readers can not do.

    Get the factory service manual from Toyota's TIS (Technical Information System) via the 2-day subscription ($2p). Comprehensive diagnostic trouble shooting tree listed for every code.
    Toyota - New Subscription

    You may have to convert CHM to PDF, if you wish to save the files.
    Toyota TIS download tips | PriusChat
     
    #12 exstudent, Sep 16, 2018
  13. Patrick Wong

    Patrick Wong DIY Enthusiast

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    1. It is obvious that the inverter/transaxle coolant loop is plugged up (likely due to not replacing the inverter coolant per the maintenance schedule) and the other posters have already provided good suggestions about how to address that.
    2. The two fault codes that your car has logged relate to the inverter having failed. It would be good to clear the DTC by disconnecting the 12V battery for a few minutes, then reconnect. Then, make the Prius READY when the inverter is cold, and see if you measure ~13.8VDC at the battery. If you do, this shows the DC/DC converter is working OK when the inverter is cold.

    If you measure a lower voltage, then the DC/DC converter has failed and you should replace the inverter. Then you don't have to worry about cleaning out the cooling passages of the original inverter. However you should still force clean water through the transaxle coolant loop and the associated radiator until you have clear water coming out.
     
    #13 Patrick Wong, Sep 16, 2018
    Last edited: Sep 16, 2018
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  14. sleeperbot

    sleeperbot Junior Member

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    Thanks all. I ordered a VCI/Techstream when I ordered the Haynes manual. Should have that soon. I've got an old laptop I can run it on. Appreciate the links to the TIS!

    Unplugged the 12V for several minutes then reinstalled. With the car in Ready (and cold) read 13.83V at the terminals. Some good news there.

    Power flushing the radiator and transaxle is a little involved. Won't likely be able to get to that for a few days.

    Posted via the PriusChat mobile app.
     
    #14 sleeperbot, Sep 16, 2018
  15. sleeperbot

    sleeperbot Junior Member

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    Glory to God in the highest there is turbulence in the tank!

    Found time two days ago to try and clear the system with water and compressed air. Fun times! Though not as thorough a tear down as I wanted. Still no motion in the tank. So I put it back together and let the Blue Devil flush soak. Now there is clear circulation in the reservoir!

    Going to let it sit another day longer and do a couple more drain and fills then replace the coolant.

    Praying the upcoming test drive will show no damage to the inverter.

    Posted via the PriusChat mobile app.
     
    #15 sleeperbot, Sep 19, 2018
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  16. sleeperbot

    sleeperbot Junior Member

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    Ok, so went through and blew out the radiator and inverter and flushed them with water. Everything was put back together and the system has nice pink flow visible in the reservoir tank like it should.

    Test drive went fine until about 10 minutes in. At about 65 mph with the a/c on the car threw up a Red Triangle. The engine gave a loud whine and the energy diagram in the MFD showed no power going to or from the HV battery. Regenerative braking did not occur either.

    Pulling over to check the coolant flow found it still steady and good. Read the codes with Torque Pro:

    P0A78 and P0A94, just like before.

    Any other items to consider before pulling the inverter?

    Posted via the PriusChat mobile app.
     
    #16 sleeperbot, Sep 25, 2018
  17. sleeperbot

    sleeperbot Junior Member

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    Wanted to add a P.S. to this. Replaced the inverter. Seems to be running fine now. Thank all for your help!
     
    #17 sleeperbot, Oct 7, 2018
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