Please help me understand cooling in Clarity.

[Landshark]

I was also thinking about this, and here are my thoughts.

Honda provided these instructions for a few reasons:

1. The HV system exists and needs instructions on how to replace the coolant.
   
   
2. Something happened to the HV coolant system, like the system started leaking or physical damage occurred to the coolant system.
   
   
3. The HV battery needs to be changed.
   
   
4. The car is very old or the mileage is high. (That's a good question: when does this condition happen?)

Furthermore, Honda's recommendation to test the coolant for proper concentration is based on prevailing weather conditions. For instance, a car operating in an Alaskan winter with very low temperatures would require coolant with a high concentration.

Less than 2 weeks ago you initiated this thread out of concern for changing the coolant at 100,000 miles. Now you seem to be trying to convince yourself that it isn’t necessary. “Oh, that information about how to change the coolant isn’t relevant to my situation”. At least that’s how is comes across, multiple reasons why you don’t need to do it.

Even the 50/50 coolant blend recommended for non-Alaskan environments can become weak and in need of some concentrate to restore its original strength. Testing it after 3 years and annually thereafter would be a wise practice. Our motorhome requires 10-11 gallons of coolant. It is relatively simple to replace, but somewhat costly due to the sheer volume. I test it annually and add concentrate as needed.

 

[Joe17]

Me personally, I would not change my EV coolant. Only the engine, and then only if it's needed not based on some abstract time in the manual. The manufacturers often are very conservative with their schedules.

 

[Hoon]

My 2019 has 65k miles so I thought I should do the coolant change. I only intended to do the engine coolant and not touch anything on the other area.

Draining and filling the main radiator was pretty straight forward. However, after everything the heater would not work anymore. Every time I change the temperature from LO to just 1degree higher, I hear the heater trying to run and a loud liquid gushing noise. I knew it was air pocket that is causing the problem. I quickly turn off the heater to prevent any damage just in case.

I had run the engine even for 3+ hour trips and then only had to add a bit more coolant through the reservoir, so maybe the engine was okay without any air pockets, but the heater was still not working. Later I found that you have to use the maintenance mode (up up down down left right left right ...) to force the pump to circulate when doing coolant change.
I was relying on normal way (HV charge mode like 10 minutes) to let the engine temp rise (I get to 180F in about 5 minutes) and waiting so the coolant would start circulating, but apparently that wasn't enough. Maintenance mode will turn on the water pump even while the engine is cold so that will purge all the air very quickly. After using maintenance mode, the reservoir was at low so I topped it up and now the heater is working again and no water gushing noise.

While at it, I also removed the front area cover under the hood and topped off the other reservoir and accessed the bleed screws just to make sure. The tiny reservoir (I think this if for the battery charging) was very low, so I'm glad I topped up that one. When plugging in the charging plug I used to hear loud gurgling noise and I feel like that has also reduced.

Anyone needs to see photos, let me know. I'll be able to upload them later.