manu, je ne veux pas polémiquer, je cite juste une partie du manuel d'atelier :
"The system is pressurized by the radiator cap to suppress boiling and the resultant air bubbles which can cause engine overheating. As the engine warms up, the coolant in the radiator and the water jacket expands. The excess coolant flows through the radiator cap and hose to the reserve tank to be stored there temporarily. Conversely, as the engine cools down, the coolant in the radiator and the water jacket contracts, and the stored coolant flows back to the radiator from the reserve tank. The radiator cap has two valves. One is a pressure valve which holds the pressure in the system when the engine is running. When the pressure exceeds 93.3 ? 122.7 kPa (0.95 ? 1.25 kgf/cm2, 13.5 ? 17.8 psi), the pressure valve opens and releases the pressure to the reserve tank. As soon as pressure escapes, the valve closes, and keeps the pressure at 93.3 ? 122.7 kPa (0.95 ? 1.25 kgf/cm2, 13.5 ? 17.8 psi). When the engine cools down, another small valve (vacuum valve) in the cap opens. As the coolant cools, the coolant contracts to form a vacuum in the system. The vacuum valve opens and allows the coolant from the reserve tank to entertheradiator."
désolé, c'est en anglais, mais je crois qu'on comprend...