2001 mini over heating- cooled car off- filled overflow- started car- started to heat up- stopped engin- cooled off- refilled overflow- steam comming out of overflow when car is started

Pull off an upper radiator hose and fill until it starts to come out. Connect the radiator hose and fill the overflow tank and gow for a short drive to heat things up. Let cool, check the overflow tank and refill. The cycling of heating up and cooling will purge air from the system, you just need to keep adding fluid to the overflow tank.

Get the fill container replaced as soon as possible!! It's an easy job to do yourself.
Drain the coolant, replace the container, refill the system. Run the engine until at working temperature. Turn it off and let it cool down then re-check the coolant level.
If you are running the vehicle with not enough coolant you are basically 'cooking' the engine!
Running an engine 'Too hot' can cause parts to heat to the point where they will weld together causing Expensive damage.
Coolant runs at around 100*C so some steam is expected. If there is a lot of steam get the vehicle to a Good mechanic.

Over heating the engine is a serious concern. With the hood raised you should hear the motorized fan turn on just behind the radiator as the engine requires additional cooling.. If you look in from the rear of the radiator you should see the fan blades.

This electric powered motor operates on a thermostat and when the engine temperature rises this fan should come on. I'm assuming from your description that when driving and air is flowing through the radiator as the car travels the engine is nor overheating.

Check fan motor thermostat, check fan motor and check wiring.

Wiring Diagrams related to the Honda Civic
http://www.wiringdiagrams21.com/category/automotive/honda-automotive/civic

Motor engine cooling fan only runs as engine temperature requires additional cooling.

You have a vapour lock. The coolant isn't flowing. The remaining water is not cooling your engine evenly so you could crack your engine block. The water that isn't circulating turns to steam. The water pump could need replacing if the impeller failed. You may need a new thermostat. Get someone knowledgeable enough to fill your radiator properly and then keep the overflow reservoir filled to half. Check that bottle at least every week.

Most cars have an 2 electric fans on the radiator. One will run when the coolant gets hot and the other will run when there is more cooling demand OR it will run when the AC is turned on. My guess is, the second fan is not running when your AC is. Your AC system creates heat of its own. The heat is removed through the condenser (radiator-like coil) which is usually located in front of your engine radiator. Without a fan the heat is transferred into your engine radiator causing it to over heat. This would explain why it overheats while idlling and not while driving. While driving, air is flowing through the radiator and condenser. to provide the necessary cooling. In short, check to see if both fans are running when the engine is hot and the AC is turned on.

You still have a lot of air in the cooling system and you have to speed up the water pump to get any coolant to flow through the heater. Let the engine cool off, then open the radiator cap and top off the radiator. Pour the coolant in at a rate slow enough to let the air bubble up without splashing the coolant back out. Once you get the coolant level up to the top overflow hose, the remaining air will be pushed out by expansion through the overflow tank once the engine gets hot, and will be replaced by coolant from the tank on cool-down.

If everything is working correctly; thermostat, heater core, water pump, head gaskets, etc. Then that leaves the radiator cap, the overflow hose or the overflow tank as being the problem.

As the engine heats up the coolant expands flowing into the overflow tank. As the engine cools the coolant is drawn back into the engine from the overflow tank. but this depends on the vacuum created by the cooling liquid. the radiator cap has a "valve" that lets pressure out and vacuum in. If it fails then you may not achieve a good vacuum. The hose that connects to the over flow tank must be non leaking as well; if it leaked then coolant would not be drawn back into the engine, only air would be sucked in. And lastly the coolant has to be drawn from the bottom of the overflow tank. again we dont want to be sucking air.

Some engines require a vent screw to be opened when bleeding the air out of the engine.

If you dont have an external coolant leak anywhere under your hood that has shown up on your driveway it could be the intake manifold or the headgasket leaking. Also check the thermostate to solve the heat issue.

check your antifreeze level. It's probably low. if you add to it and it doesn't fix it you may have air in the system. Wait for the car engine to cool, remove radiator cap and start engine. the fluid will start coming up and you should see bubbling. Shut engine off before it overflows. if you didn't see any bubbling there likely wasn't any air in the system. if there was bubbling fill the antifreeze to fill line again and repeat process until no more bubbling. make sure to let engine cool before taking off cap.

Flush rad & change coolant & thermostat. Check operation of rad fan, & make sure it is coming on when engine reaches normal operating temperature. Be sure to bleed air out good when refilling rad/cooling system. Start engine & turn heater on when refilling & let rad fan come on & off at least 2 or 3 times before putting cap back on rad, and refill rad as needed as you do this. then fill return bottle to proper level & see what happens.