Hot or Cold?

[Averroes]

Hope everyone’s well. Wanted to ask, do
I add coolant to the coolant reservoir when the engine is cool and fill it to the max line? Or do it when the engine is warm and fill it to the max line?

Car in question is a 04 Corolla, the coolant reservoir only has a low and max line. Thanks in advance for the help.

 

[oldhp]

I've always kept the level between Min / Max when fully warmed up. When overnight cold the fluid level should be close to the Min mark to allow for coolant expansion.

 

[joegreen]

Sometimes there is a max line for hot and the max line for cold.