Help! Coolant Overflow Empty

This past weekend I did a coolant flush and refill. Today (4 days later) I checked the overflow tank and noticed it’s pretty empty. I did some research and it says or should be at least 30% full. Is it normal that it’s pretty empty or should I get this checked out?

 

No leaks?

It's possible that when you refilled the system there was air that found its way back out, and the system sucked down the coolant from the reservoir.

As long as you aren't finding coolant on the ground, top off the overflow bottle and radiator when the engine is cool. Check back in a few days

 

No leaks that I know of, the car runs great too. I also didn’t mention that when I checked it today the car was cold I hadn’t turned the car on for at least 3 days. Can it be that when it’s cold it’s low and once I turn the car on it will fill up?

I will have it checked out tomorrow just to be safe.

 

Just add a little more. As said, coulda been an air bubble. Besides...you cannot over fill it. It will spit out what it doesn't want.

 

And yes, the level in the bottle will be higher when the engine is hot. The radiator cap will let some coolant out to maintain the right pressure, then when it cools off it'll suck it back into the radiator.

Like doubleduty said, there's no danger of overfill besides a bit of a mess

 

Definitely keep the level in the overflow tank up to the FULL line. At the VERY least, make sure the fluid is well up over the bottom of the rubber hose that runs down from the cap. As the cooling system "burps" out air when you drive it, ie, it get's hot, as is normal, then cools down again when you stop it for a while, like a couple hours, it will draw coolant in from the recovery tank. You want enough in there for it to draw in..
When it cools off, if any air had bubbled out, the radiator will draw coolant in from the recovery tank to replace it. That's why to keep coolant in the recovery tank. Otherwise it just sucks air back in. Makes the cooling system less effective. Air don't cool as well as water do!

If you don't "burp" the cooling system yourself after a drain-n-fill, it WILL burp itself over time as you drive it. Just check on the recovery tank and radiator to ensure they have enough coolant in them. The first few times you drive it, you WILL need to add coolant to the recovery tank, very possibly to the radiator as well.
An easy way to check the radiator fill is to give the upper radiator hose a good squeeze when it's nice and cold. If it squeezes flat, or just squeezes easily, there's air in the radiator. Add coolant to the radiator, and top up the recovery tank.

No matter what, keep the recovery tank topped up to the FULL line when cold. Always keep it topped up.

Ok, ok, I shut up now...
Pat☺

 

Thanks @PhantomTweak

 

Agree, check it before running for the next few days and top off the overfill before running each time. Also, take a peak at your water pump, and pink stuff around it? I had a thread recently where I was trying to diagnose if there was an issue, but traded in the 4Runner before figuring it out.