It all works fine. During the winter I have none of these problems. And in summer it only happens when I'm stuck in traffic, while when I'm on cruising speed everything is fine and the temperature remains steady at slightly above the halfway mark.

I'm worried with the fact that a guy has replied that I have a cracked block. But if I do have a cracked block, then why does this happen ONLY when I switch off the engine when the temp goes at exactly below the red mark?

Till now, thanks for your help