The thermostat is located at the rear of the engine. The exhaust cross over pipe that goes between the exhaust manifolds makes the thermostat housing hard to access. The easiest way to change this thermostat is to first remove the exhaust shield and exhaust cross over pipe, then the thermostat can easily be changed. After changing the thermostat, be sure to bleed the air from the system. Look for bleeder screws and run the heater until air blows warm.