Classic Prius Coolant Replacement

Got around to changing mine last night. I noticed that the bleeder closer to the car's left side is on the pressure side of the system, and if I just leave that one open while the key is on it will constantly circulate fluid back to the reservoir and burp out bubbles. That's a lot more efficient than the manual's tedious turning the key off to open the valve and maybe let out one bubble. (It helps to secure the tube in the reservoir well enough so when it burps out a big bubble it doesn't jump out and squirt coolant around.)

The bleeder closer to the car's midline is another story as it's on the suction side, and opening it while the key is on will tend to draw fluid in (and then air, if you let it get that far). But it only seems to take a few inches of vacuum to overcome the suction and get fluid flowing out from this bleeder too. I didn't measure the vacuum needed, but was able to supply it by mouth without effort. (No, I'm not an alien that can drink ethylene glycol; I just used a long clear tube and watched where the fluid was.)

Probably a tube on this bleeder long enough to siphon down into a coolant jug on the ground would work, and then you could have a constant flow out from both bleeders while letting the pump run (while having to carefully watch and refill the reservoir since this coolant wouldn't be recirculating). I may try that next time. Or just an extra little pump on this bleed line (an old windshield washer pump?) and run it back into the reservoir too.

Even with just one bleeder open while the pump was running, I found I could make progress (relatively) quickly by reaching around and grabbing and shaking and squishing all the inverter-related hoses, and bouncing the car up and down. Still took me two or three hours, but some of that was figuring out what was possible and what seemed to work.

-Chap

 

I think that you win the prize for the shortest elapsed time changing the Classic inverter coolant. It is interesting that you determined one valve was on the high pressure side and the other on the suction side.

 

Right, certainly you can't just leave the suction side bleeder open drawing air in. You want coolant to be flowing constantly out from both bleeders. On the pressure side you get that for free whenever the ignition is on. On the suction side you need to arrange enough suction (sucking out) to exceed the pump suction (sucking in). A bleed line with its own little pump running back to the reservoir would be ideal, but failing that I thought there might be enough height for a bleed line siphoning down to a jug on the ground to be enough. I did not try either idea, so there's still room here for somebody to do a proof-of-concept.

Of course with coolant being siphoned into a jug on the ground, somebody would need to watch the reservoir closely and keep it refilled.

Since what's needed really is constant suction/flow, obviously sucking on the tube is not a workable approach, just something I did (very briefly and carefully) only to feel how much suction was needed. Please nobody repeat that at home.

-Chap

 

I forgot to follow up here when I went back and measured the pressures: about 18 inches of water at the high-side bleeder, and about minus 10 at the low side. The bleeders are more than 10 inches above ground, so yes, a siphon down to a jug on the ground should be adequate to move coolant in the right direction out the low-side bleeder.

-Chap

 

My experience is that this wasn't enough. Partly because I feel like you need to remove the bleeders and install teflon tape. If you open the suction side bleeder enough to get a flow, it appears to me that air is sucking in through the bleeder threads (ie. bleeder is too loose)... I just created more air when messing with those bleeders and only worked the pressure side over a few days.

I was thinking about trying an aquarium pump with the coolant pump not running.

 

Hmm, interesting problem. You know, downstairs in the goo department I think I've got something that would be just the ticket, once sold by Permatex under the name "Hylomar HPF". It's a fine viscous blue goo that never sets or hardens, yet seals like you wouldn't believe, and resists automotive chemicals including glycols. I can't seem to find it sold by Permatex anymore (my tube I've got to have had for 15 years or more), but it is apparently still available directly under the Hylomar brand here. (Apparently what Permatex was selling was the Advanced Formula, but the original Universal Blue would probably be even better suited to the job. I see here the shelf life is supposed to be two years, but I just squoze some out of my 15-year-old tube and it doesn't seem to have changed a bit.)

Probably something less exotic like Permatex 14 would work just fine too, considering it only has to seal threads against a suction of ten inches of water.

This almost makes me want to go out and put some Hylomar on my bleeders right now to see what happens, only it's dark out.

-Chap

 

Huh? 3 hours is short? I have filled the coolant twice on my classic, the first time I had it at a slight angle (the front wheels of the car where 3 inches higher than the rear, by driving the car up on a makeshift ramp from 2 pieces 2x4 nailed together staggered to have 2x 1.5" threshold that is easy to drive up on.
I have never bothered to read the manual how to get the air out of the system, so I use my own method which takes approx 1/2 hour and I never turn the car on until everything is as good as it gets:
After draining and closing everything again except the inverter coolant reservoir cap, pour in coolant until the reservoir stays full. Then grab the two larger hoses that go to the radiator (don't confuse with the engine coolant hoses) and carefully alternate, then simultaneously squeeze those hoses to push the coolant back and forth. Every time the reservoir burps and empties itself, refill close to overflowing and again start careful massaging the tubes, going more vigorous to agitate the fluid and bring air to the surface. Once there are no more large burps I carefully open one bleed nipple (without tube or anything, just venting air to the surrounding air) until the first drop of coolant shows up, close it again and do the same for the other nipple.
With the nose of the car slightly higher this simple procedure allowed me to get *all* air out of the Classic inverter coolant loop - I never had to refill the reservoir after this ~1/2 hour tube-massaging procedure.
The second time I did this the car was level and it took much more effort to get the hoses to burp, but with more vigorous squeezing and occasionally flattening as much as possible of one the larger tubes with both hands, most air came out and I was done in about 1 hour, after that I simply drove the car and the next 2 days I had to add about a cup of coolant each day from the bubbles finally finding their way to the reservoir.
Hope this helps others to make this a little easier.

 

Guess they moved their web site. Try here.