Curious what coolant level you like on a cold engine. Truck came with Coolant at the level Full line but I was getting overflow. I have my level now set right in the middle of Full and Low and no more overflow.

Anywhere between Min and Max.


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Thanks - seems others found the same.

I would like to find the time to read more about cooling systems in general. I remember some vehicles had a fan which ran even after the vehicle was turned off.

The radiator should be full (up to the neck) and the overflow reservoir should be at the full or max line when cold.

This is in the manual.

Don't overthink this.
Although the physics of the cooling system is complex, we need not go that far.

Basically the coolant expands as the engine warms up, the coolant goes thru the vacuum valve in the radiator cap and into the plastic overflow tank. The level will rise with a hot engine.
When the engine and coolant cool down and since the overflow hose is immersed in the overflow tank, a vacuum is created and the coolant is sucked back into the radiator/expansion tank.
This back and forth movement insures that the radiator/expansion tank is always completely full and void of an air.
It also insures that coolant is no longer spilled onto the ground.

And this is why the overflow tank should always have coolant covering the overflow hose, preferably at least at the min level, but not so much that it runs over to the ground.

Decided to actually find it for you. Pages 412 and 514 of the owner's manual.

2021 Toyota 4runner Manuals & Warranties | Toyota Owners

Thanks for the quick chalk talk.

Owner's manual is clear and thanks for finding the pages.

I am getting overflow on my 2023 Limited, took some coolant out of the overflow tank, now is 2 fingers when cold and about 1 finger when hot below the FULL line. It´s only been 2 days, usually the overflow mark (coolant debris in the cap) is seen weeks after I clean it so I can´t still be sure this level will work. Full level at cold doesn´t seem logical because the level rises when hot. It´s not the first time the owners manual is wrong, maybe a translation error, who knows. Although leaving it full at cold would only leave a trace of dry coolant, no big deal.

Just make sure it is never below the bottom line when cold.
Simple as that.

Yep, you got it right