Just check your overflow container after a few days, if there is any air in the system it should work it's way out and just bubble in the overflow tank. If you see the tank level drop and you don't have any leaks, then there was some air. It is not a major concern.
If it makes a boiling sound when it comes out then it is probably a bad radiator cap.
Probably a head gasket problem or a cracked head. Sorry for the bad news.
Probably need to add antifreeze. Check the Radiator not the overflow tank. If you are low on antifreeze it will not circulate through the heater core.
Honestly I think that Pontiac made the overflow reservoir too small. I have to add antifreeze to my GF's Grand Am once every couple months. If its a consistent problem where you're having to add antifreeze daily/weekly the car may be running too hot, and should probably be looked at by a mechanic.
I'm not sure about a Honda Accord, but all cars are pretty much the same. You can remove the radiator cap and add antifreeze, or you can look for the antifreeze "overflow reservoir". A piece of tubing from near the radiator cap should run to a plastic jug about the size of a gallon or two. It usually sits off to one side or the other under the hood. The side of the overflow reservoir may have a fill mark on it. The top should have a lid that is easily removed. That's probably the recommended place to add antifreeze.
If there is no leak visible so you can see antifreeze under the parked car, you probably have a head gasket going bad. You may have some signs of steam in your exhaust, or at least a sweet smell coming from the exhaust. You should have a compression test done on your engine. That is exactly what the overflow reservoir is for. When the engine is hot, excess coolant goes into the overflow tank, as the engine cools,it draws coolant back into the radiator.
If you mean the fan blows but sometimes the air is cold, it probably is low coolant (antifreeze) level in the radiator. Check the level AT THE RADIATOR, not the overflow tank, while the truck is cold.
The antifreeze should be diluted How much is up to you. Also be sure to configure in the location where you live (hotter, colder) as this also makes a difference I'm pretty sure that antifreeze needs some water to work properly (activates chemicals in antifreeze) If you went 70% antifreeze & 30% water you should probably be fine no matter where you live. ========================================================== Ford vehicles come from the factory with a 50 / 50 mix of distilled water and the correct type of antifreeze for the vehicle . Ford states not to exceed 60% antifreeze in the mix
The type of antifreeze to use for a 2001 Mitsubishi Eclipse is one that is mixed 50/50. Most antifreeze brands will work. The Prestone brand of antifreeze is probably the most expensive.
At a BMW Dealership or online is probably the easiest.
Antifreeze should show up to the level line when cold normal but may raise some when hot and fall below some when cold. This is due to expansion and contracting from engine being hot or cold. A slight fall below this line can not mean much it can also evaporate some. A small leak can loose some but if you are putting fluid in everyday or two then you probably have a leak someplace.
This is probably an overflow pipe from the cold water tank in the loft.