how high should be the pressure in the cooling system?

[Camry-rulez]

How Hi should be the pressure i the cooling system. on the radiator cap and the manual says that the max pressuer is about 1.3 kgf/cm3 (18,5 PSI). I ask because when my engine is hot then the uper hose (from engine to radiator) is a little bit harder than if the engine is cold. Is this normal? or is mayby the radiator cap bad?

[toyomoho]

Normal, when the engine is cold the coolant system is not pressurized.

[Camry-rulez]

and what is making that pressure??? why does the cooling water expand while it is going hot? I thouth that it is not normal that when the engine is at normal temp. that then the houses can be a little bit harder.

[toyomoho]

The system is much like heating water on the stove. The water starts to steam then boils and if left unchecked all the water will boil out of the pan. Water boils at 212F.

If the water is placed in a pressure cooker it will still heat up but the gases can not excape. The result is an increase in pressure inside the cooker. If the water is now pressurized it can become hotter then 212F because the boiling temp is increased..

The cars coolant system contains flexable hoses, these hoses become stiffer as the pressure inside them raises.

[Camry-rulez]

OK, Im very happy about this answer thx