auxiliary pump problem

yes air bubbles can cause problems. But you most likely just didn't put enough coolant in your car. Open up the radiator cap (the actual cap and not the reservoir) and fill it. Many people run into this issue on the 2nd gen Prius, either they didn't fill the actual radiator or they didn't put enough fluid in. It can take 3 to 4 days of filling every morning to get the correct amount of fluid in the car.

 

Did you use a scan tool to read the trouble codes that activated the "RED Alert"? If so, what are the codes?

 

Generally with the air bubbles in the red business on the dash you don't get any codes but if you look at the freeze frame data and coolant temps you'll see that something gets in front of the sensor or the sensor gets sitting in air shoots the temperature sky high then a few seconds later that bubble moves or something moves the light goes off everything is normal in the car and then 30 seconds a minute later it comes back on again regardless of speed and a lot of cases and you're just doing this in the cyclic manner while driving The car is not really overheating the air bubble is messing with the sensor and it spikes the sensor the wax the silicone whatever moves in there and so on and it just goes on and on and on I got a car doing this right now It's never hot nothing is hot nothing not even the hoses The bottom hose won't even get water warm to the aluminum radiator it'll take all day unless it's 80° out so here you've got to get the system full fluid standing at the top of the radiator neck almost about to fall on the ground and then that's to stay there for an hour let me know when you have that completed That's going to take a while pouring it in out of a bottle It's very slow remember water's got to stand at the top of the filler neck with the cap off for about an hour every time you walk back by the car the coolant's going to be gone and you'll pour a little more in you'll come walking back by 20 minutes and it'll be gone and pour a little more in and so on and so on check it out this might take you to 3 hours to get the car full like this then when the water or coolant mix is standing at the top of the radiator neck and it's been there an hour Make sure the reservoir is full to the lower plastics viewed through the filler neck Make sure it is full and cap everything and go for a drive now you should not see your overheat light come on coolant will be circling and cycling and you'll have heat in the normal time If you continue driving and that heat stops you have lost coolant at that point The hoses may be rock hard and everything hot as all get out but you have no heat. Let the car sit in the driveway or wherever you're at for two three hours till all the pressure is down seriously and then remove the cap slowly letting the air escape which will but no coolant and then when you take the cap off you've lost no water taking the cap off because you're doing it with your hand and now you see no water standing at the top of the radiator neck You're going to add close to a quaurt I bet