Pressure in the expansion vessel

My 206 HDI vehicle doesn't have any water leaking from the expansion tank. The temperature doesn't exceed 90 degrees. There is no water in the oil. However, this morning, when it was cold, I decided to check the water level. The water level was at maximum level. It had risen. When I tried to start the car while it was cold, it hissed with pressure and released water. I shut it off and used it immediately. I don't have any problems within the city for 20 km. I will go to the repair shop for the temperature, but the technicians will directly say if it was the air that caused the gasket or something. I know it could have been the air. There was a leak in my air conditioner gasket. It was leaking. I don't know if the air is coming from there. I'm waiting for your valuable comments.

Hello, it has nothing to do with a leak in the air conditioner. Most likely, the engine overheats directly due to problems like air in the radiator, seals, or circulation system.

Our vehicles are closed systems. It's normal for the expansion valve to build up a certain amount of pressure when it's opened. After all, the water is constantly heating and cooling.

Sir, how do we bleed the air from the radiator? I know where the bleed plug is, but I don't know how to do it.