Systems and methods for diagnosing a thermostat

A method, comprising:

• interpreting engine heat data indicative of a first amount of heat introduced into an internal combustion engine;
• interpreting exhaust gas recirculation (EGR) heat data indicative of a second amount of heat introduced into the internal combustion engine via an amount of exhaust gas provided to an intake manifold;
• interpreting heat loss data indicative of an amount of heat loss experienced by a coolant, wherein the heat loss data includes an ambient air temperature, and wherein the amount of heat loss is a predefined value based on the ambient air temperature;
• determining a temperature of the coolant based on the first amount of heat, the second amount of heat, and the amount of heat loss;
• comparing the determined temperature of the coolant to a sensed temperature of the coolant;
• and
• determining a status of a thermostat responsive to the comparison.

A system, comprising:

• a liquid cooling system including a thermostat, the liquid cooling system structured to circulate a coolant;
• an exhaust gas recirculation (EGR) system structured to circulate an amount of exhaust gas;
• and
• a controller operatively coupled to the liquid cooling system and the EGR system, wherein the controller is structured to:
• receive engine heat data indicative of a first amount of heat introduced into an internal combustion engine;
• receive EGR heat data indicative of a second amount of heat introduced into the internal combustion engine via the amount of exhaust gas;
• receive heat loss data indicative of an amount of heat loss experienced by the coolant, wherein the heat loss data includes an ambient air temperature, and wherein the amount of heat loss is a predefined value based on the ambient air temperature;
• determine a temperature of the coolant based on the first amount of heat, the second amount of heat, and the amount of heat loss;
• compare the determined temperature of the coolant to a sensed temperature of the coolant;
• and
• determine a status of the thermostat responsive to the comparison.