Teach me about Water Pumps /Coolant Pumps in The Prius

For one don't replace coolent or flush it a pain to get air out
Under the driver side head light the 2nd one you can hear it when you turn the car off saving the heated coolent. In case your going some ware soon. If loud just clap hoses and swap hose fast. The add coolent in each of the 3 cooent holder one under the black cover the radiator

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There is!

It's just that there are also three more.

I assume the one you replaced was the one on the front of the engine, driven by a belt.

That's the one that circulates the coolant through the engine to keep it cool when it is running. Naturally, it does no pumping when the engine is stopped, because the belt is not turning.

But sometimes, in cold weather, you would like to have heat in the cabin, even though it is a Prius and sometimes the engine is stopped. So, there is a second, electric pump, called the "A/C Water Pump", that just runs when the engine is stopped and you have the heat turned on, to keep the hot coolant flowing through your heater. That is why a Prius can keep such a comfortable, steady heat in the cabin, even though the engine starts and stops.

Before the Prius, there were some high-end luxury cars that had such a pump, so you could enjoy comfortable heat for some length of time with the engine stopped. As a Prius owner, you have that as a standard feature. And you have it even better: it isn't just "for some length of time", because as soon as the coolant is no longer warm enough, the engine simply restarts, and shuts off when the coolant is up to temperature again.

Also, you have a Gen 2 Prius, which has another interesting feature: a large thermos bottle under the left fender. It keeps hot coolant in there (can stay hot for a day or more!) so that when you go to start the "cold" engine, it can just have the stored hot coolant pumped in, and already be partially warmed up. There's an electric pump that does that, called the Coolant Heat Storage Water Pump. Keeping count? Three pumps so far.

Finally, the electronics and transaxle have their own cooling system, completely separate from the engine. It has its own separate reservoir (which you fill with the same type of coolant). That has its own electric pump.

Four pumps shalt thou count, and the number of the pumps shall be four.

The best, quick way to get a jump on that is called the New Car Features manual for your model, standing by for your reading pleasure at techinfo.toyota.com.

-Chap