Engine cooling system diagnostics

摘要

A single pressure transducer tapped into the cooling system of an engine, downstream of the pump, is used to measure coolant pressure at high idle and coolant pressure at low idle while the water temperature is such as to assure the thermostat is closed; the pressure readings are equivalent to the pressure across an orifice or restriction formed by the coolant bypass when the thermostat is closed; the combination of high idle pressure and difference between high idle pressure and low idle pressure permit diagnosing whether the pump is faulty or whether there is unduly large restriction in the engine, which otherwise could not be known with a single pressure reading.