Resolved What is the Purpose of Coolant Overflow?

[habitatguy187]

Topic says it all. The reason I ask is because this weekend I drained most of my coolant (long story) and didn't have any extra so I filled my car back up with water. (Filled it up all the way)

So after boosting a lot on the way home today I park my car, come inside and go back out after about half an hour, and there's coolant everywhere. It was too dark to check and make sure everything was hooked up properly (almost CERTAIN it is) but I was thinking maybe it's cause I put in too much coolant (water). Note that it didn't do this when driving regular. Thanks

 

[19Eclipse90]

Recall that liquids expand when heated and condense when cooled (generally).

When the coolant is heated, the pressure and volume increase. So that you don't blow a hose or radiator, the increased volume of coolant will dump into the overflow. When the coolant condenses, the pressure decreases and the volume returns to it's initial value. Because of this pressure decrease, atmospheric pressure pushes the fluid in the overflow back into the cooling system. If your overflow is filled properly when the motor is at room temperature, there will be no air flowing into or out of the cooling system -- only coolant.

It sounds like you had air in the system initially that was pushed out or expanded and pushed coolant out and caused a spill. Know that this is also a loss of volume in the water, so chances are you have more air in your system now

...At least, I think that's how it works...

 

[Boost92awd]

^^^ Yeah that pretty much sums it up. Good post.