inverter coolant bleed

Discussion in 'Generation 1 Prius Discussion' started by ronlewis, Mar 4, 2026 at 3:49 PM.

  1. ronlewis

    ronlewis Active Member

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    OK, what am I doing wrong? swapped a brake actuator into this car, which required removing the inverter, coolant lines, and a water pump below it. Lost a good bit of coolant in the process, maybe a beer can's worth, no more than two. Now, I got it back together, filled the reservoir, and coolant is not circulating in the reservoir, but I hear the pump running and squishy sounds.

    Got two clear hose stuck on each bleeder screw looped over to the reservoir. When I loosen the bleeder screws nothing much happens. The right side has pushed coolant about halfway to the reservoir, then stopped. Nothing has come out of the left bleeder screw.

    I've turned the key to ACC and let the pump run for a minute, bleeders shut. Turn the key off, open the bleeders and nothing. Did the same and left the key on, nothing. Ran the engine for several minutes, turn it off and open bleeders, nothing. Actually ran the engine with bleeders open, nothing.

    I'm guessing the system is air locked. How do I "jump start" it so that coolant circulates enough to expel air bubbles.

    One note, when I loosen the right side bleeder, a little coolant leaks from around the threads. Is that where I'm losing my air?

    Also, coolant level has dropped a few times, and I've topped it up, probably about a beer can full.
     
  2. ChapmanF

    ChapmanF Senior Member

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    The extra fun part about bleeding the inverter loop in gen 1 is that the two bleeders connect on different sides of the pump. The one closest to the fender connects near the discharge (pressure) side of the pump, so you can go ahead and open it while the pump runs, and stuff will come out.

    The one closest to the middle of the car connects near the inlet (suction) side of the pump, and if you open that bleeder up while the pump is on (without making careful arrangements), you let stuff in. If the stuff you let in is air, your bleeding job becomes eternal.

    If you follow the steps in the repair manual, Toyota wanted you to turn the car on, running the pump, turn it off, stopping the pump, open the bleeder, close the bleeder, repeat. It's tedious as all get-out.

    It turns out the suction the pump produces is about −10 inches of water (relative to the open reservoir), and that bleeder is more than ten inches above the ground, so if you want a less-tedious way to bleed the loop, you can do it ➡this way⬅. That link also talks about the leaks-around-the-threads issue.
     
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  3. ronlewis

    ronlewis Active Member

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    OK! Let me try again. Thx.
     
  4. ronlewis

    ronlewis Active Member

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    LOL, I'm being ignorant again. I still wasn't seeing any movement, so I was trying to siphon air out of that left bleeder. I got an empty liter bottle, poked a hole in the cap big enough for my hose, and filled it half way with coolant. With the other end on the closed bleeder, I turned it upside down to fill the hose with coolant. Set it on the ground and opened the bleeder, and sure enough, it starts sucking bubbles out of the bleeder. I've done that over and over, probably 20 times.

    On the pressure side, I'd let the pump run for a minute, then open the bleeder, and nothing. Tried a few times, never saw any significant amount of coolant in the hose, and no bubbles. Left the pump running, same thing. So, I started sucking on the hose, like I siphoning that side as well, and I'd get lots of bubbles. Did that 20x or so as well. Going back and forth between the bleeders, and keeping the reservoir full.

    Never did get the reservoir to circulate though, and I'm not sure if I wasn't just sucking air from the leaky threads on the pressure bleeder - didn't have anything to seal it with. A couple of times and got that bleeder hose to fill up and actually pump coolant out without me sucking, and the bubbles stopped. And the passenger hose quit showing lots of bubbles, but it never did just flow on its own.

    Anyway, it got dark so I quit for the night. Not sure if I'm making progress or not. Need to get some sealer for those threads - will plumber's tape work? That liter bottle seals up nicely - doesn't leak when I hold up upside down to drain coolant into the hose. Wonder if it needs to have a vent hole to siphon properly. Seems to work the way I'm doing it. Bubbles definitely coming out of the bleeder. Just seems like I would have gotten all the air out by now. I can't drive it right now - I got a rear axle hub off and the new one doesn't come in until Monday. I've started the engine and let it run a while, but that doesn't seem to do anything. On the pressure side, does the end of the hose need to be submerged in coolant?

    Definitely got the taste of coolant in my mouth, but haven't swallowed any.