What is up with my car? My '11 Cruze has been losing coolant, a lot of it, but I can't see any leaks from inspecting the engine, and it's making a rattling noise. The noise seems loud at times, and other times not so bad. Going on the highway though, it's not as strong as it used to be, it takes double the time or more to get to 65mph for example. What do I do? Thanks guys.