The radiator features a crossflow design, complemented by a Coolant Reservoir that accommodates coolant expansion at elevated temperatures and allows for easy monitoring of the coolant level. An additional heat exchanger, known as the ATF cooler, circulates automatic transmission fluid (ATF). N51 engines are equipped with a manganese oxide coated radiator designed to minimize ambient air ozone, utilizing an Environmental Air Catalyst (EAC) sensor to ensure the special coated radiator is properly installed. The EAC sensor is hardwired to the radiator, preventing disconnection, and can be replaced only once in the event of failure; subsequent failures necessitate replacement of both the EAC sensor and the radiator. This sensor continuously sends a signal to the engine control module, which will activate the check engine lamp if an uncoated radiator lacking an EAC sensor is installed.