Your coolant is evaporating in a faster rate. This could be because of a poorly maintained antifreeze system, damaged components, or a quick change in driving style. When the antifreeze level drops without an evident leak, these parts could be to blame: Driving uphill, transporting large loads, a defective EGR (Exhaust gas recirculation) system, and a worn-out water pump are some causes of excessive coolant loss. Some vehicles need specialized pumps like this one.