The purpose of the cooling system is to absorb excess engine heat, which is then dissipated into the air via the radiator. In fact that's the wrong word for it because heat isn't radiated at all. It's convected.

Bleeding the cooling system is straightforward. Do not run the engine whilst your doing it. Remove the highest component on the cylinder head such as the coolant temperature sensor, and fill the system until coolant comes out. If possible hold the expansion bottle as high as you can whilst filling. Air cannot get trapped because the flow and weight of the coolant will force it out. The reason for this doing this is because when the engine is cold the thermostat is closed, and the cooling system is effectivly divided into two parts. With the system closed air in the block will have no means of escape, and so that's why you have to remove the highest component. Refit the component when the cooling system is full.

The water pump is a centrifugal pump which aids circulation. Coolant is drawn into the centre and thrown outwards, hence the term centrifugal. Such type pumps will not draw air and push it out, and so running the engine will not achieve anything. The pump needs to be completely submerged in order to function correctly.

Make sure the cooling system is clean and clear, and that the radiator is clear. Use an airline and blow through the fins to make sure they're also clear. If the radiator is blocked it will not dissipate heat. If you have air conditioning make sure the condenser is also clear. Dust and dirt in the fins will restrict airflow and seriously affect heat dissipation. If the radiator is cold to the touch when the engine is fully warmed up then you have a problem, and the fan won't cool the engine if there's no heat in the radiator to draw away.

Start the engine once you have filled the cooling system and allow to warm up. Cooling system pressure and temperature are directly proportional to each other. The pressure in the cooling system should increase with the temperature. When the thermostat opens the pressure will fall slightly as heat is given off in the radiator. The pressure will then continue to rise as the temperature rises, until the fan cuts in and heat is drawn away. The pressure will then fall as the engine cools, and this process is ongoing.

Hope it helps.

If you still have the original radiator it could well be furred up, if that is the problem the temp should be OK when driving gently with a good airflow through the rad but will get hot if you push it hard.

Allot of feedback so far! Thanks for explanations railroad! This car has no expansion tank it's just on the side if the radiator. The radiator is 10 years old and might be clogged but seems to be warm, I have flushed it with quick flush but it did not get all the corrosion out.

Would it be OK to remove the radiator take a hose and try to back wash everything through the radiator and block? Then fill with fresh coolent?

I should just order a new radiator then! It just seems so stable at 105'c I just thought it would over heat, what your saying is the rad might be half blocked at work at 40% effiency

Does the fact that changing the blocked heater matrix improve it slightly prove anything?

Thanks for the feedback railroad!