I just bought a new 2007 Yaris (has 5000 miles) and i've only driven it for 3 weeks now and about 150 miles and this morning going to work (about a 5 min drive) the coolant light came on. I checked the level and it was at HIGH. Is that ok or what could be going on? I don't want a car that overheats on me before I've made my first payment!