Finally got around to flushing coolant, used tips from my prior thread and here: https://www.wristtwisters.com/forums/...ush-33648.html

Went pretty well, I changed the thermostat and O-ring while I had the system drained (had a couple of small leaks when really really cold outside this winter that I solved by tightening down the housing bolts a little more that I wanted to take care of). However, both times when I filled it with water (without the thermostat in) it wouldn't take more than 2/3rds or so of a gallon of water. Also, when draining it, quite a lot would not come out until I removed the thermostat housing. On final fill of the system including reservoir, I still have about a quart left in the bottle. Now, I haven't taken it for the final ride yet to try to fully bleed down the system, but is this normal? I did run it for about 4 or 5 minutes, but the level didn't seem to go down (and this happened on all the water flushes as well).

Sounds pretty normal to me. Mine never takes much more than that to fill after draining. There must be some pockets that don't fully drain.

If I remember correctly from when I did it, there is a lot that remains trapped in the hose leaving the water pump.

From re-reading the manual just not, apparently Honda thinks that's OK, as I pretty much followed that procedure.

Do I really need to raise the tank again and add more coolant once the air is out of the system, or will it draw coolant in from the reservoir like most other systems will?

It will draw from the reserve tank.

But only if you have enough in the system to create sufficient pressure/vacuum in order to draw from the reserve tank. How much is sufficient? Who knows?

Nonetheless, thanks for the post. I wonder if I should tackle this job as well before hitting the track.

Whenever I have refilled after draining and run the engine for a while I have had to only add a couple of oz. I would think you would be OK counting on the reserve tank for makeup. Just make sure that you fill at the cap under the tank.

Just do a quick check... Its only one bolt to get the tank up... Also the 3.7 quart or whatever figure they give is for the engine and reserve tank as that's exactly what fit in mine when I did it.