[Wolverine51]

Page 571 of the Owners Manual says :

"Only a properly trained technician can
refill the coolant and check the system
for leaks"

I wonder why this isn't a DIY job

And nowhere do I find whether replacement of this coolant should be done at a certain age or mileage point (maybe when engine coolant is replaced?)

 

[Verdier]

I could be wrong but I'm under the impression the inverter coolant is the same as the coolant used in the radiator. In fact it might be part of the same system like on my 2004 Prius. As far as DIY, I don't think any manual tends to say that for some obvious reasons including keeping their dealers in business doing all that for you. I'm sure a smarter user will correct me if I'm wrong on all this.😊

 

[PacketPaul]

On the Prius it was a bit tricky. There are two coolant pumps, an electric pump and a manual pump. You had to pull a relay to deactivate the electric pump or it may randomly start pumping. Toyota specified using a special computer tool to perform the work, but in reality a jumper wire could be used.

The process was drain the coolant, and refill (as normal). Then bleed by running the electric pump. You ran the electric pump by using a jumper wire on the now bare relay pins. Fill, bleed, fill, bleed. Once you knew the trick of pulling the relay and using a jumper to activate the pump, it was an easy process.

My biggest concern with this vehicle is the lack of a shop manual. There is also no knowledge pool as with the Prius. Hopefully over time both items will be rectified.

 

[Mobilcams]

I have gone on long trips and popped the hood to “check” things under the hood. I have not once felt the reservoir feel remotely hot to the touch. What conditions will make it heat up? I’ve checked it from freeway speeds where the system cycles between battery and engine, and in city driving where I wasn’t trying too hard to be green (sport mode).

 

[insightfully]

Regarding Inverter Coolant, this (non-Honda) Insight serviceability article mentions that the Inverter and DC-to-DC converter are liquid-cooled, and the electric motors are cooled by the automatic transmission fluid... so the article recommends a more aggressive/earlier transmission service (2 yr/30k mi) than Honda does.

The Insight carries 2.3 qt of automatic transmission fluid, and is one of the items that can show up on the Maintenance Minder. In severe driving conditions (hills and low speeds), Honda recommends the transmission fluid gets changed at 47.5k miles or 3 years. I think the manual suggests "properly trained technician" since it's an infrequent and high-impact service.