I tried to do a search on this question, but couldn't find anything.
Lately my low coolant light has been coming on, but the fluid is at the right level. I went to check the radiator, and when I take off the radiator cap, you can hear coolant being sucked back into the overflow neck. Is this normal or is there something not right? The radiator was full also. Thanks, Tyler

 

There should be threads on low coolant light i did change my sensor, but my coolant is always full and i made sure all the air was burped out too,n now my light doesn't come on no more

 

I know I will need to check the sensor, but I'm concerned with the coolant flowing back into the overflow only after the radiator cap is opened. Is this normal, or is there something going on with the flow of the coolant?

 

What do u mean by the coolant coming to the overflow is it coming out ,bcuz when the radiator is full the extra coolant or water it has it stays in the overflow but shoebox n Fred are knowledge experts about that

 

What I mean is that it seems like the radiator holds all the fluid. If I open the radiator cap, I can hear coolant being sucked back into the overflow.
It all started when the low coolant light came on. I added some coolant, and started it up again. Light still on. So I opened the radiator cap, and hear the coolant being sucked back into the overflow. Some came spilling out the top. Just wondering if it is normal or not.

 

There is no way coolant can be "sucked back into the overflow". I'm assuming by overflow you mean the reservoir under the battery. That's an open, vented system - can't develop a vacuum. As the coolant heats up it expands. This builds pressure in the radiator. With a stock cap the cap allows the expanding coolant to escape into the reservoir when the pressure reaches 18psi.

When the coolant cools down and contracts, the radiator develops a vacuum and the cap opens to allow the vacuum to pull coolant from the reservoir to keep the radiator full at all times.

Are you sure what you hear when you loosen the cap isn't the pressure from hot coolant flowing past the cap and into the resrvoir. Or the vacuum from the cooling radiator pulling air into the radiator past the loose cap?

 

I'm not sure. All I know is that when I opened the radiator cap, I heard coolant moving, and then some coolant spit up through the overflow neck. I assumed coolant would be flowing from the radiator into the overflow.
If I'm reading you right Injuneer, this should be normal? I did it when the coolant was still somewhat hot. The coolant must be moving past the cap when pressure is broken, and flowing into the overflow?

 

The inner cap has two springs in it. One spring pops the valve in the cap open at 18psi pressure. The coolant flows through the valve into the annulus between the cap and the fill neck, and goes out the hole through the rubber hose to the reservoir. The second spring opens the valve when the radiaotr pulls a vacuum, and the vacuum pulls the coolant up out of the reservoir, through the hose, through the connection on the fill neck and through the inner cap.

If the springs are worn out, the cap may not hold adequate pressure to keep hot coolant from boiling, and spitting out into the reservoir.