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inverter coolant change: alternative method with no bleeding

Discussion in 'Gen 2 Prius Main Forum' started by alekska, Nov 20, 2010.

  1. alekska

    alekska Active Member

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    Hi All,

    Unlike "standard" drain and refill coolant replacement, which require difficult air removal procedures, I did the replacement in a different way.

    I took a large syringe and removed ~ 250 cc of the old coolant from the expansion tank, and then refilled with new. Then I started the car (to READY) and let it run for some time. Pump was running so new coolant got mixed in. Then shut down the car.
    Thus I repeated the procedure several times, until I used all my new coolant (a gallon, or 3.8 liters). Of course, every next step after the first one some new coolant was removed together with the old one, and the ratio was increasing, but I did calculations and it turned out that with 0.25 L at each removal removal and total amount of new coolant of 3.8 L and system capacity of 2.7 L I ended up with 67% new coolant in the system. All took me probably 1.5 hours.

    This is good enough for me for now, and if I want better I would do it again with another gallon of SLLC. That will end up with ~ 12% old coolant in the system and 88% new.
    I would argue that even with a standard drain and fill there will be some old coolant left in the system (say, 270 cc = 10% seems reasonable ) which will result in 90 % new coolant in the system.

    I thought I would share this, so if somebody is not comfortable with all that air bleeding etc., and possibility of overheating expensive converter and motors, they can consider replacing coolant in this way.

    Thanks,
    - Alex (2005 Prius with 112000 miles)
     
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  2. bisco

    bisco cookie crumbler

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    my dad had a late sixties wagon that burned a quart of oil every 500 miles. he never changed it, just kept adding new. the thing is probably still running somewhere.:D
     
  3. dogfriend

    dogfriend Human - Animal Hybrid

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    My dad had a Chevy truck like that. He just kept adding oil to it.

    The OP reminds me of the DIY method to do a Auto Trans "flush". You drop the pan and replace the filter, then refill the pan again. This replaces about 1/2 of the total volume, the rest is trapped in the valve body and torque converter. Then you remove the external cooler line and start the engine so that the old fluid is pumped out into a container while you add the same amount of new fluid to the fill tube. You keep replacing the old stuff with new stuff until the fluid coming out looks as clean as the new stuff going in. It takes a little more fluid than the total capacity because of mixing of the old and new fluid, but its preferable to disassembling the entire transmission just to get all the old fluid out.
     
  4. Hal W

    Hal W New Member

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    Good way to do it, think I'll do the same thing. I hate bleeding air out. Thanks for the idea. H
     
  5. Patrick Wong

    Patrick Wong DIY Enthusiast

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    It really isn't that difficult to get the air out of the system, when doing a 2G inverter coolant drain and refill process. (Classic is much harder.) However, if the OP's process encourages owners to do the inverter coolant change rather than ignoring that service procedure and hoping for the best, then that definitely adds value to the community.

    I don't know about the assertion that 270 cc of old fluid would be left in the system (that would be ~9 US fluid ounces, or 3/4 of a soda can's contents.) The most likely place for fluid to be trapped would be in the hoses leading to the inverter coolant pump. However when I replaced the pump in my 2004 (after first draining the coolant) almost no fluid came out of the hoses as they were disconnected from the pump.

    The relatively difficult 2G process is getting the air out of the engine coolant loop when doing a drain and refill due to the presence of the coolant heat recovery system canister and pump that must be manually activated to refill the canister.
     
  6. uart

    uart Senior Member

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    Good tip alekska. :)

    I just re-did alekska's calculations to confirm that he calculated/estimated the concentrations correctly and yes the figures checked out.

    If anyone is interested then attached is the XL spreed-sheet result for the concentration of new coolant (volume new : total volume) for up to 44 iterations of the procedure (not that you'd probably want to go that far). The calculations of course assume that the new coolant is very well mixed with the existing coolant before the next iteration is begun.

    BTW. The first column shows the relative concentration of new fluid, that is vol_new : vol_total. The formula I used "fx" is shown in the highlighted cell.
     

    Attached Files:

  7. David Beale

    David Beale Senior Member

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    There is a "no bleed" way to change coolant that many shops use. You disconnect the coolant hose and connect a "diverter" in its' place. This device diverts the vehicle coolant into a canister and replaces it with new coolant from a second canister. When the new coolant runs out the diverter valve is closed. You then shut off the engine and remove it, reconnecting the hose.
     
  8. andyprius

    andyprius Senior Member

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    2nd. Para, "Expansion Tank" ???? I hope you are talking about the Inverter Coolant Reservoir. :cheer2:
     
  9. seilerts

    seilerts Battery Curmudgeon

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    With Super Long Life Coolant in the inverter cooling system, it is virtually impossible to tell the old apart from the new. On most cars you can add some distilled water before adding the new coolant, so as to identify the transition, but I wouldn't try it in this case.

    IMHO, an AirLift is the best tool for this job as well as coolant refilling on just about any type of vehicle. I love tools that turn a tedious, multi-step, time-consuming process into a 5 minute job.
     
  10. Mendel Leisk

    Mendel Leisk Senior Member

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    Why do you replace only 250 cc at a time? Does the reserve tank have signif. more capacity?

    Also, I think doing this all in one session would increase the odds of the new and old coolant not mixing completely. Alternately, just doing this once a day if you're a daily commuter, I think you'd getter better mix, and avoid burning fuel idling.
     
  11. andyprius

    andyprius Senior Member

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    The only problem with this system is I noticed a considerable amount of debris when I drained the system, this debris is still at the bottom of your inverter. I had no problem refilling with coolant, I just attached the right size plastic hose to the bleed nipple and watched the air bubbles and filled as necessary. The real struggle was getting the air out of the engine cooling system. You should do both. :D
     
  12. alekska

    alekska Active Member

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    Yes, sure. I just thought it also serves as expansion tank when coolant warms up. There is even overflow tube, draining toward back, right on several electric connectors :)

    - Alex
     
  13. alekska

    alekska Active Member

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    The tank does not look that big... I did not want to risk letting the air to the tubes.
    And you are right, my calculations did show that if you use bigger single drain volume, you get higher percentage replaced at the end.
    Also, everyday drain/add should work good, you just need to lift the hood and unscrew the cap every time :)

    - Alex
     
  14. SageBrush

    SageBrush Senior Member

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    I like this idea for the engine coolant.
     
  15. andyprius

    andyprius Senior Member

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    Which will equal even more debris not flushed out.:D
     
  16. edthefox5

    edthefox5 Senior Member

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    Whats the most disconcerting is the aluminum salts debris
    found in my inverter coolant tank at 20,000 miles. You know the white stuff in the top of the tank and on the cap. There is definately some aluminum corrosion going on in the Inverter and was mentioned in a Hobbit Inverter teardown also. Its not horrible but something is going on.

    I wonder if this aluminum corrosion has something to do with the Inverter coolant pump failing so frequently? Eating up the bearings in the pump? Only a pump autopsy would tell.

    At 20,000 I did what the OP did only used this product:

    Red Line Synthetic Oil - Water Wetter® Coolant Additives - Water Wetter®

    This product has some good anti-corrsion properties. At 30,000 miles so far so good I see no salts.

    I'm running a bottle in the engine coolant too.

    At 50,000 I will do a full replacement on both. But so far so good.
     
  17. Aaron

    Aaron Member

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    Will coolant added to the overflow reservoir eventually work it's way into the radiator/engine?