The cooling system is among the most neglected maintenance areas on the typical family car, which is why coolant-related failures account for a disproportionate share of roadside breakdowns and a significant portion of preventable engine damage. The system is invisible in operation — the coolant temperature gauge sits at normal, the heater works, and there is no obvious sign that the coolant circulating through the engine has degraded to the point where it is no longer doing its job adequately.