Peugeot 306 radiator bleed

model, I'll give you a source here. The place like the valve cover in the picture is taken by opening it. open this cap, put a bottle or a can under it. The purpose is to keep the flowing water there. Then start the vehicle and when it comes to 90 degrees, it starts to throw air mixed with water from here. When the air runs out and pure water starts to come, you stop the engine and close the lid.