Prius gen 3 not taking enough coolant after flush

Be sure to leave the cap off to initially bleed a gen3. The year helps as early gen3s are different. A good drain may only produce 1.25 gallons and takes some time. Ideally you measure the volume removed but you were probably low.

It is possible to have an electrical issue with the pump. You won't have movement of engine coolant until the thermostat opens.

 

What year is the gen 3 you're changing coolant on?

2010 and 2011 model years have a bleed screw, which should be left open during refill (to allow air to vent freely during the fill process), at least till coolant starts flowing out. It's directly above/behind the EGR cooler/valve, a black plastic junction with a white screw cap (which is the bleed screw. There's also a spigot you can push a piece of clear tubing on, basically to avoid spillage.

For model year 2012 on, there's a similar junction, albeit WITHOUT the bleed screw. I think in that's your case you could pull off a coolant hose at that junction, just leave it off while you fill, till coolant starts coming out.

Attached is Repair Manual excerpt with the engine coolant instruction.

 

You need one of these Airlift type tools. Changing coolant and getting all the air out takes no more than 15-20 minutes.

They even sell one at Harbor Freight.

 

I've only changed mine twice, soon to be 3 times, and have not had any problems.
Maybe they are filling too fast? I go very slow, and squeeze the hoses.
And after driving it for 5-10 minutes and letting it sit overnight, I've only had to add a cup or so.

 

I have never had an issue with air bleeding. It bleeds itself within a cup by simply pouring in the coolant. It might drop a half inch when the thermostat opens and flow is observed from the bottom reservoir hose. No flow and no code? I would "cool it" until the thermostat is replaced.

Does the fan ever come on? Does it energize with the ac? If its no in either case, fix the fans. Check for power at the fan connector. Power is there? Change the fans.

 

What I would like to see is the corresponding Repair Manual excerpt for model year 2012 on. Did they decide they didn't need the bleed valve because bleeding works well enough without it? Or do they actually say to take a hose off?

 

So it's not this easy?

 

It's really about as easy as what he does, but it's not what he does. Kind of weird to see a "Toyota Master Diagnostic Technician" ignore the repair manual like that.

Unless I missed it, he didn't point out where the B line on the engine coolant reservoir is, or what it's for.

There is a line marked "B" that is up above the line marked "FULL". To fill and bleed the system, you pour coolant in all the way up to the B line, install the reservoir cap, and run the engine in maintenance mode all the way up to full operating temperature and at least seven minutes longer.

During that time, you can watch air bubbles being delivered into the reservoir through its top hose, and the coolant level dropping down closer to the FULL line, as it is trading places with the air.

When you shut it off, it may still look a bit above FULL because the fluid is hot, but let the engine cool down again to ambient temperature and, if your experience is anything like mine, the level will be right at FULL like the engineers had the whole procedure dialed in. (If it ends up below FULL by a bit, you just top it up to FULL at that point. I've never had to.)

I'm not saying other people can't have success doing it other ways than what the manual says, but that's the procedure in my 2010 Toyota repair manual and hasn't ever let me down.

Because my car's a 2010, I have the bleed valve in that hose tee, which the manual says to have open while filling the reservoir. They removed that valve for 2012. I'm still curious to see what the procedure changed to in the 2012 manual. Maybe that's what the guy in the video was following?

 

Yes it is that easy. The Op is not getting radiator fans to come on. He is either not waiting long enough or he has a fan oriented problem.

Both the mechanic and I leave the cap off while its bleeding.

 

I noticed that, which is why I added the info that the repair manual explicitly says to put the cap on, and that the repair manual method has worked well for me.

That never means there aren't other methods that people can have success with, but readers are entitled to know how the manufacturer said to do it, and make their own informed choices on alternatives.

Easiest, most convenient access is probably at the relay sockets. I've had for many years an old-school "remote starter" button (just a comically oversized pushbutton with several feet of wire and a couple of clamps, made to clamp onto an old car's starter solenoid and easily crank it from outside the car). That, with a couple terminal-sized metal blades to stick in the relay socket, makes a tidy way to test various relay-controlled things.

Of course you still then have the socket itself and the little run of wiring from there to the fan included in what you're testing. There's nothing tricky about testing right at the fan itself, other than maybe cramped access getting to its electrical connector.

 

The ac compressor has to be on to engage the radiator fans, not just the ac blower fan.

I would check the power at the radiator fan cable. Fans do go bad. When the fans are on low they are wired in series. So one bad fan will keep both off. When commanded high, each fan independently gets full 12v power.

I prefer diagnosing with a voltmeter rather than jumping power at relays because a wrong jump on a relay coil could damage the ecm. Jumping directly at the fan with the cable disconnected is safer although it is usually redundant at that point.