Actually, it always is when operational. The pressure is what moves the refrigerant or coolant (depending on whether you're referring to the air conditioning or the engine cooling system) through the system.
The pressure raises the boiling point of the coolant.
It Will usually have an air pocket in the cooling system. But it may just be the Air Conditioning equalising after you shut the car off. Start by filling the cooling system
If there is no cooling system, the engin will overheat.
The cooling system helps keep the car from running too hot. A diagram for the 1998 Ford Taurus cooling system can be found in the car's maintenance or repair manual.
Yes, engine oil and automatic transmission oil can both get into the cooling system.
Your engines head gasket is blown. This means a cylinder will lose a little compression because gas can escape into the cooling system. Doing so forces oil into the water, and water into the cylinder when the piston is on the down stroke. This overheats your car puts extra stress on your cooling system because it becomes even more pressurised (you will need to top up the cooling fluid very frequently because of this). Get it fixed as soon as possible before you do more damage to the cooling system or the engine. Your mechanic will know that the oil and water in the car will also need to be flushed once the head gasket is replaced.
A cooling system schematic for this car can be found in the maintenance manual. It can also be found in the repair manual of the car.
yes the air con on a car is presurised
It usually means that there is a faulty head gasket, but it can also indicate a particular kind of leak in the water pump.
Poor coolant circulation in the cooling system.
A "professional flushing of antifreeze" is when a mechanic or other paid professional connects a hose assembly to your car radiator while at the same time opening the release valve (usually located at the bottom of the radiator) and forces water thru your car's water cooling system. The effect is to cleanse the system of old and rusted water and old antifreeze. This procedure is usually done just prior to adding new antifreeze to a car's cooling system, most often before the winter driving season. The end result being a more effective cooling system for the car. Hope this helps.
drain the whole cooling system and refill it. You will never know if you don't give details of your car!
The cooling system is a closed system. If there is smoke (probably steam) there must be a leak in the cooling system somewhere.