Engine and inverter coolant flush drain plug locations?

Not sure about that type, but I keep the Pentosin Pentofrost A4 on the shelf. It's the premixed version and runs about $25 for a gallon jug. It's essentially equivalent to the Toyota Super Long Life Coolant. Carried by many autoparts stores.
I believe they also have concentrated versions available.

 

Not sure about that type, but I keep the Pentosin Pentofrost A4 on the shelf. It's the premixed version and runs about $25 for a gallon jug. It's essentially equivalent to the Toyota Super Long Life Coolant. Carried by many autoparts stores.
I believe they also have concentrated versions available.

 

Pentosin A1 is offered as prediluted and as a concentrate. It is the equivalent of Toyota Long Life Coolant, iirc.

Is there a reason you need to have the concentrate?

 

In Gen 4, no need to flush....the two drain valves (on driver's side of radiator) drain both systems almost completely if you just let it drain for a long while (and open the radiator and caps on tanks.)

Last year, the 2017 drain/fill took a gallon and a half of Toyota Super Long Life coolant. Specs says 6.6 Qts so sounds like I got all of it out.

 

I wouldn't bother, just drain and fill, with 50/50 Super Long Life Coolant, keeps it simple. Introducing water into the equation is a can of worms, best avoided.

Judging from the Repair Manual, the inverter radiator is at the bottom on this gen, and drain is accomplished by opening a spigot on it.

For both engine and inverter changes, see attachments.

BTW, this is a 4th gen Prius? Your avatar doesn't show anything.

 

Between 2017 and 2021, Toyota added a radiator cap to the Prius...not sure why...so engines may or may not have one in certain models.

 

This is what I got out, albeit of a gen 3:

- engine coolant drain: 4.25 liters roughly
- inverter coolant drain: 1.5 liter roughly

With gen 3 there's a drain bolt on the bottom of transaxle, probably get most due to that, vs draining from the transaxle/inverter rad.

 

There is quite a bit of travel from heat exchanger to other various areas where you will not be able to drain which an engine block drain probably won’t help. If you really want to go that route, there probably is some hose you can open up.