Help....inverter coolant not flowing even after pump change

Ticklefishdude · Jun 23, 2017

Hi - Bought a 2005 Prius and replaced some HV battery cells and works great. Been getting the P0A93 code. I replaced the inverter cooling pump. Still got it. Thought it would be crazy that the hoses could be mixed up but upon inspection, the hose coming from the coolant reservoir goes down to the bottom of the radiator and not the coolant pump itself? Are there any exceptions to the diagram that was provided in this thread? I can't see why. There is very little flow in the reservoir and when I utilize the bleed screw, it seems that the main fluid in the radiator goes down. Before re-routing stuff, I would like your input. Love the car otherwise - Thanks!!!! John

Maria98 · Aug 3, 2019

Jim Caldwell said: ↑

Its an 09 Prius. Has 100K miles on it. I have in the past several weeks made three 350 mile trips, car ran perfectly. I have Techstream, and the car hasn't been setting any code except for an evaporative fuel system leak. It was time to do an inverter coolant change. I drained about 2 qts....that is all that would come out (and yes the bleeder valve was opened) Refilled it with Toyota SLLC. When topping off, using the procedure where you put a tube on the air bleeder valve and put the other end into the open reservoir), I notice that coolant would not rise up more than a couple of inches in the tube....bubbles came out, but it would never pump any fluid up into the reservoir, although the reservoir was about full. I then looked in the reservoir, and the coolant had not dropped an appreciable amount, and was absolutely still. Not the slightest ripple indicating flow. So I grounded the car and ordered a new pump (Gates brand) from Rock Auto. I should have thought about "how is it that it is going hundreds and hundreds of miles with no inverter coolant flow?" I guess.
Well, I installed new pump. Still have zero flow visible in reservoir, and never any fluid rising up in the bleeder tube, and the level in reservoir never drops! I did hear a very loud noise from the new pump after hitting the start button twice to make it run, this lasted only about 1 or two seconds, and thereafter it was quiet....like abnormally quiet, no funny sounds of air in system or anything....but it is definitely running, there is a quiet smooth sound and you can feel the vibrations.So I drained coolant again (this time oddly only 1 qt drained out). I removed the new pump intending to determine if either the old or new pumps are pumping or not, as it seems like there is a blockage in the system. Wish I had a pressure gauge to see what is happening on the discharge side, whichever it is.
I looked up this system in the Bentley manual, and it has one short paragraph and one illustration of the system....It covers the earlier generation only through 2008 unfortunately, so I am uncertain as to whether significant changes to the inverter cooling system were made in 2009. But from the diagram, there is no valve to control the flow at all., no valve that could possibly be closed.
This appears to be a simple centrifugal pump, which means it should not be damaged by a discharge blockage. I need to operational test these pumps. I put two sections of tubing on the old one, and (guessing) put one end in a tub of water. It pumped no water with either of the two pipes on the pump submerged in the tub. Then it occurred to me that its not going to pump unless the suction side is primed.....have to figure out some way to do that. But I am not even sure which is discharge and which suction.
I also thought about the possibility of an air lock, the pump not working before it was uninstalled, due to no prime. I think it must have been full of fluid, as I could squeeze either hose right next to it, and the level in the bleeder tube would go up and down a little. It also stays very quiet as I said, not starting to make a loud racket from bearings running dry.

Can I test it for a blockage by forcing some compressed air into the pump tubing, with reservoir cap and bleeder closed??? Is safe?

I also would like to know if the car will shut down with the triangle of death with an overtemp of inverter or MG1/ MG2? Or just set codes for same, or problem with coolant flow or temp?

Update to my first post.....I got new pump tested operationally, and it's not really running at all. After I installed it, I sure THOUGHT it was running but it didn't turn at all during the operational pumping check, and after that I checked with an ohm meter and it reads up in the megs with either polarity! Will probably never deal with Rock Auto again, but their parts have always been reliable and good in the past. Needed this car fixed badly, now it will be days longer. Now I am wondering if the original pump died thousands of miles ago! Because I read elsewhere in this forum that even if no coolant is being pumped, the car continues to operate sometimes for a long time nevertheless...until the car gets particularly stressed on a hot day.
I think the original pump was not really the original....I know there was a defect in the 09 inv. coolant pumps, and Toyota replaced them under a "recall" or something. I bought the car at 50K miles, 50K miles ago. Well, the mechanic who did this replacement--- or SOME replacement--- believe it or not, had cut both power wires a few inches from the pump....when I peeled off the ordinary junk cheap black electricians' tape, the mechanic had just stripped the ends of the copper wire and twisted them together, then taped them No boutt splice or solder! Of course the wires were corroding. But not so badly yet that there was a bad connection, dropping voltage. Still....what kind of idiot would do this with a vital electrical component which has to work to prevent failure of a 2000.00 electrical component? They did wire it up with black to black and white to white, so reversed voltage wasn't a cause of failure (connector will only go on one way, the right way)
Click to expand...

Now I`m facing the same issue in my Prius 2008 , could you please tell me if you fix the issue I will be thankful for you

Help....inverter coolant not flowing even after pump change

Ticklefishdude Junior Member

Maria98 New Member

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Help....inverter coolant not flowing even after pump change

Ticklefishdude Junior Member

Maria98 New Member