I have a Chevy Joy, which is the hatchback model of the Monza, which looks very much like the Opel Corsa B and uses the same parts.
My car has a metal radiator and the engine was substituted for a Nissan B14.I just got the engine replaced three months ago and the head gasket is intact.
The normal safe temperature on my car is a quarter on the gauge. If it passes this, that means that the car is overheating and the needle then continues to the red zone if I leave the car on.
The radiator loses water and I refill the secondary bottle once every five days.
If I let the water fall below the secondary bottle and more than half of whats left in the radiator, I need to disconnect the hoses in the radiator to flush out the water, then reconnect it and refill. If I do not do this, I get 'air pockets' in the radiator and the radiator pushes back up water with bubbles.
When I on the air conditioner, the water level in the radiator lasts longer (i.E it does not leak).
However, when I on the a/c, the radiator gets hot, and the temperature gauge passes quarter and goes right into the red zone after about 20 minutes. The water/coolant levels in the radiator remains but the temperature is very high until I off the a/c and shut off the car to cool off.
Also, when I brake very sudden, the temperature gauge goes past a quarter, and onto half/three quarters and I have to wait for a while before it returns to normal.
The coolant fan spins.
The A/c (until the car overheats) blows cold air in when it is working and when I am driving. But when I stop for lights or traffic the air being blown out is not soo cold.