I have a 2002 Mini Cooper. I noticed that over time i would have to put a small amount of coolant in the reservoir every now and then. Never was an issue and the car ran fine. This morning however, on my way to work, I noticed that the heater was only blowing cold air. Then my temp gauge would shoot up. I made it to a gas station, put some coolant in, but it's not cycling into the engine...even after it heats up. Is this a bad thermostat? Also, is it hard to change a thermostat. I tried following the top radiator hose. It looks like it goes under the manifold. Not sure where to look. Help is appreciated