If you are sure you have no visible leaks;































Check your engine oil - if it is muddy brown - your coolant is going into your engine - head gasket, cracked head, etc. Bad news.































Also look in the radiator - take the cap off when the engine is cold - is it full? - if you see oil spots in the water you have a head gasket or head problem.































If you see coolant then try running the engine with the rad cap off - if it blows bubbles in the radiator, same problem.































Look for white smoke behind your car - sure sign of coolant getting into the combustion chambers. Coolant burning smells kind of sickly sweet.