When I was checking all the fuilds yesterday I noticed that the antifreeze was down to the add mark on the overflow bottle. I fired it up and opened the radiator cap and all looked good, no bubbles or oil. I ran my errands and when I got back checked the overflow bottle again and it's a couple inches above the add mark. When I tried to open the radiator cap to first notch antifreeze went all over the place. Is this normal while the engine is running or do I have a problem?