Easy Peasy: Partial Engine Coolant Exchange

This was performed on my Prius (v)agon, and is so far as I know identical to the Gen3 Prius.
Rather than drain all the engine coolant and then fight the plumbing to get rid of air, I decided to exchange 1 gallon a year from 50k miles on the odometer without letting any air into the system.

This was a 5 minute job, exactly as easy as I expected (and that so rarely happens!)

Tools:

1. 1 ft length of plastic tubing 5/16 inch ID. I did have to dilate the opening of the hose with a needle-nose pliars and lubricate the drain tube for it to slide on to the drain tube. Cost 35 cents at a hardware store.
2. Container to accept 1 gallon of old coolant. I had an empty one gallon container of coolant from a prior exchange -- perfect.
3. One gallon new SLLC (I use Zerex Asian.)
4. Funnel

Steps:

1. Raise front of car, place jack-stands
2. Attach hose to drain tube, and put other end into drain container
3. Fill up most of reservoir
4. Open Pet-cock by hand. I inserted my hand into a larger opening nearby and reached the valve easily.
5. Add coolant to reservoir as it is draining. The drain is slow enough to easily do this with only one person, but since this was the first time I attempted this method my wife added the coolant to the reservoir. I'll guess that it took at least 3 minutes (and perhaps 5) to drain and replace the gallon. I think the Pet-cock was fully open.
6. Pet-cock closed, hose detached.
7. Reservoir closed
8. Coolant disposed of correctly (down the drain with copious water dilution.)
9. End of story

It used to be (back in the Gen2 era) that the inverter circuit was easy and the engine circuit a PITA. Now it is reversed because the inverter exchange requires removal of the under-engine cover.

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Photos:

1. Taken from the front-driver corner, showing where the drain and pet-cock are located. A plastic tube is attached to the drain through a hole in the under-engine cover.
2. Looking up through the hole in the plastic engine cover, the drain tube and yellow pet-cock (handle) are seen.
3. Engine Coolant reservoir