I’m guessing that Texases is right (as usual) about the “temperature regulator thingy”, and that the "master cylinder and gaskets) is probably the headgasket. It’s entirely possible that there is a communication/translation difficulty messing up the terminology. It’s even possible that they actually use totally different terms, like the English do.
Your car doesn’t know when to “drink” water. The cooling system is a closed system, with basically a radiator, a thermostat, and a water pump. When the engine reaches full operating temperature, the thermostat should be fully opened and allow th epump to pump the coolant through the engine where it picks up heat and into the radiator where it dissipates it. The thermostat prevents full flow of the coolant until it reaches full temperature.
Full temperature is typically in excess of 200F. Unless the ambient temperature where you are reaches over 200F, your engine needs the T-stat to reach proper operating temp.