Complete coolant flush with thermostat replacement, did you use 3 or 4 gallons of antifreeze?

[airdzi]

2010 LX570 w transmission cooler and rear heater.

Draining radiator and both sides of the engine block I got 3 gal (approx. 12 quarts) of coolant out. I read likely on this forum or the club that it takes just over 4 gallons.

Where is the 4th gallon of coolant? I was prepared for over 16 quarts with 5 one gallon jugs.

I truly took the time draining the system as my replacement thermostat suffered 3 day usps delay.

I know I got no air in the system as my front heat came back almost instantly.

Where is the extra gallon of coolant hiding?

I suspect rear heater and transmission cooler. I also wonder if the post I read about 4 gallons involved leaky radiator swap.

I warmed up my car again today to open the thermostat with both front and rear heat on and will check the fluid again In the AM but assuming i did everything correctly all you need is 3 gallons of replacement stuff and that also includes filling the reservoir to the F line.

Also took car for a test drive and with thermostat open coolant maintained 177-179 degrees F.

 

[Ratchey]

I swapped my radiator out. I ordered 4 gallons and don't have any left so must have used it all.
I know I didn't put in all 4 when I was finished and even after I took it for a drive to warm it up. Based on a suggestion of doing an aggressive test drive I found the over flow bottle empty and the tank a bit low.
Not sure if that info is of any help to you.

 

[airdzi]

I swapped my radiator out. I ordered 4 gallons and don't have any left so must have used it all.
I know I didn't put in all 4 when I was finished and even after I took it for a drive to warm it up. Based on a suggestion of doing an aggressive test drive I found the over flow bottle empty and the tank a bit low.
Not sure if that info is of any help to you.

Thanks, overnight it went down about half way in the reservoir so I added little bit more.

Guess we can safely assume coolant change as per FSM replaces about 75% of coolant in the system.

That actually could be why Toyota recommends first coolant change after 100k miles and following changes after each additional 50k.