Added coolant, now there's a sloshing water sound

Just one thought, the spec'd fluid, Toyota Super Long Life Coolant, comes pre-mixed, you're not supposed to dilute it further. There is another Toyota Coolant that doesn't come pre-mixed, is compatible, but just not rated as long a lifespan.

I'm guessing you got some air into the system, especially if it sounds different. You could run through the last steps in @NutzAboutBolts engine coolant change video, basically putting the car in Maintenance mode, letting it idle, keeping it topped up. Maybe helps to "burp" the hoses as bit?

Video #11 here:

Nutz About Bolts Prius Maintenance Videos | PriusChat

 

Take the cap off, open the bleeder on the heater hose. Power on the car. Then, when you see coolant at the bleeder, close it off, and top off the tank and close it off. That should take care of it.

 

Oh, hey: he has the bleeder; commencing in 2012 it's nixed.

I don't understand that. I know with various Hondas, as you pour in the new coolant mix, you can feel a strong gush of air coming out. Unless that doesn't happen with the 3rd gen Prius (due to the lack of radiator cap and the reservoir tank being the only place you can add coolant??), why would you nix it? If there's air coming out in a gush as you pour in coolant, that's good.

 

And the tank, believe it or not is actually lower in the car then the EGR cooler. So the sound of water he’s hearing is either in the heater core or EGR cooler.

In the absence of a bleeder in the heater hose, jack up the front of the car a bit, til the suspension is fully extended, wheels still on the ground. That puts the coolant tank the highest point in the system. Run the car in maintenance mode until the cooling fans cycle twice. Once is probably sufficient, twice for good measure. Top off the coolant and cap it off with the front end in the air. Any excess will discharge out the overflow of the tank.

 

@Ragingfit posted a short video where he unbolts the reservoir and raises it, ties to the raised hood I think. Do that and crack open the bleeder till coolant comes out would be good start, then close and run in maintenance mode for a whiles longer, say till the fans come on.

Ah here:

Where he mentions "this is the problem here", he's pointing at the hoses over the EGR. And on the 2010/2011, that's where the bleed screw is.

(For 2012 onward, without the bleed screw, IF that bleed screw's effective, you could accomplish the same thing by just pulling off one of the hoses right there, quickly put it back on when fluid starts coming out.)

Again, I'm assuming the bleed screw is doing something with the Prius; it is weird that Toyota deleted it.

 

He says 220 degrees in his video. That’s ALOT. I drove mine 300 miles on the highway and saw a max coolant temp of 199. But wind blowing into the radiator at 65 mph is probably a whole lot better at cooling then the fans are. LoL I think the fans come on at 195, and off at 180.

 

Hey Mendel,
I would recommend, and I've done it, when the engine is not hot and not running, raise the tank, and pull that hose off the top of the EGR cooler, hold the coolant back with your finger over the hole of the EGR cooler, let the air out of the heater hose and plug it back on the EGR cooler after you bleed the air out. If you don't raise the tank you will let more air in. The cowl can be worked under but it's right there.
I must say, it is extremely difficult to get the air out when it's below 50 degrees because the thermostat rarely opens even at highway speeds. Whenever possible do not disturb the cooling system in cold weather.
- Fix That Prius !!!