Prius, overheating and sluggish, uphill

How many miles on the car?

I would assume that your engine coolant water pump is going bad and needs to be replaced ASAP.

Posted via the PriusChat mobile app.

 

Your car needs to go to the ER immediately.
What you're experiencing is the automotive equivalent of non-fatal heart attack symptoms that will ultimately result in a non non-fatal heart attack.
Go to an independent repair shop immediately and describe your symptoms.

Tell them that you have a 2013 PRIUS with coolant issues and you want them to do a cylinder leak-down test after they check your coolant system.
If they ask why, politely thank them for their time, pay them for any work that they have done and look for a more competent mechanic.
What you are ruling out is a head gasket failure that will only get worse and worse from the temperature excursions that your motor is experiencing.
Stay away from the dealership.

Good Luck!

 

Cool and just disappearing from the jug blowing off You know it's blowing off? You probably need to check your codes and see if you have any cylinders getting ready to misfire or holding codes for misfiring That's probably going to be next at the point of this coolant blowing off and disappearing If you are extremely lucky you've caught this early enough but it sounds like this has been something that's been reoccurring and going on semi often an engine is probably in the future of this vehicle. Beware of that

 

Because you have a 2013, Gen 3 Prius, your system doesn't have a "reserve tank"; that was an older style system where the tank was a kind of stagnant backwater that only accepted coolant expanding out of the radiator and held it to be sucked back in on cooling.

the Gen 3 cooling system is a degas-bottle system where that plastic degas bottle is an integral part of the cooling system and coolant circulates right through it. So the level showing there just is the level of your coolant; if the bottle empties, you've lost a bunch.

I wasn't quite sure how to read the multiple negatives in "it doesn't seem that the coolant ... is not returning", but anyway, knowing that is an always-connected degas bottle and not a reserve tank that anything would need to return to, the picture is a little simpler.