Not sure if it's just me but I have not seen/heard too much discussion about the cooling system. I am coming up on 190K and haven't noticed anything wrong about the cooling system, both the engine and the inverter, and don't think anything has ever been done about it. Haven't even tested the coolant to be honest. My prius is a 2008 and I took it over around 2015, and I don't know if anything such as water pump or flushes have ever been done. Is this a case of "ain't broke don't fix it" or "better get on it now"?
better get on it now. start by entering your vin in the owners website to see maintenance history, then complete everything in the schedule that hasn't been performed.
It's www.toyota.com/owners, and you can check there for its maintenance history. Also, if you're DIYing, I have some pictures I can post that should make it significantly easier to find the drains. There are three of them.
