I noticed that my coolant bottle was right full after a bit of a drive. Before I left it was right on the "Full" mark. I didn't notice any bubbles. I sucked some out and it looked clean and I could not smell anything unusuall from the antifreeze. It happened to me a few months back, but not to this extent, so I didn't think much of it. Any ideas? Trucks got 80,000Km.