When the engine is cold, check the concentration and level of the coolant at the intervals listed in the scheduled maintenance information.   See   Scheduled Maintenance. 

Maintain coolant concentration within 48% to 50%, which equates to a freeze point between -30°F (-34°C) and -34°F (-37°C). Check the coolant concentration using a refractometer. We do not recommend the use of hydrometers or coolant test strips for measuring coolant concentration.

It is very important to use prediluted coolant approved to the correct specification in order to avoid plugging the small passageways in the engine cooling system.   See   Capacities and Specifications - 7.3L.  Do not mix different colors or types of coolant in your vehicle. Mixing of engine coolants or using an incorrect coolant may harm the engine or cooling system components and may not be covered by the vehicle Warranty.

If the coolant level is at or below the minimum mark, add prediluted coolant immediately.

For vehicles with overflow coolant systems with a non-pressurized cap on the coolant recovery system, add coolant to the coolant recovery reservoir when the engine is cool. Add prediluted coolant to the maximum level. For all vehicles which have a coolant degas system with a pressurized cap, or if it is necessary to remove the coolant pressure relief cap on the radiator, follow these steps to add engine coolant:

If you have to add more than 1.1 qt (1 L) of engine coolant per month, have your vehicle checked as soon as possible. Operating an engine with a low level of coolant can result in engine overheating and possible engine damage.

Alcohol and other liquids can cause engine damage from overheating or freezing.

Do not add extra inhibitors or additives to the coolant. These can be harmful and compromise the corrosion protection of the coolant.

We do not recommend the use of recycled coolant as an approved recycling process is not yet available.

Dispose of used engine coolant in an appropriate manner. Follow your community’s regulations and standards for recycling and disposing of automotive fluids.

Vehicles driven year-round in non-extreme climates should use prediluted engine coolant for optimum cooling system and engine protection.

Change the coolant at specific mileage intervals as listed in the scheduled maintenance information. The information display may display a message to change coolant at this time. Add prediluted coolant approved to the correct specification.   See   Capacities and Specifications. 

Your vehicle comes with an engine driven cooling fan drive, also called a fan clutch. This fan drive changes the fan speed to match the vehicle’s changing cooling air flow requirements. Fan speed, fan noise level and fuel consumption all will increase based on the driving conditions that include trailer towing, hill climbing, heavy loads, high speed and high ambient temperature, individually or in combination.

The fan drive is designed to provide the minimum fan speed, and resulting minimum fan noise and fuel consumption required to meet the ever changing vehicle cooling air flow requirements. You will hear the amount of fan noise increasing and decreasing as the engine power requirements and vehicle driving conditions change as you drive. This is to be expected as being normal to the operation of your vehicle. High levels of fan noise might also be heard when your engine is first started, and should normally decrease after driving for a short time.

Fail-safe cooling allows you to temporarily drive your vehicle before any incremental component damage occurs. The fail-safe distance depends on ambient temperature, vehicle load and terrain.

If the engine begins to overheat, the coolant temperature gauge moves toward the red zone:

If the engine reaches a preset over-temperature condition, the engine switches to alternating cylinder operation. Each disabled cylinder acts as an air pump and cools the engine.

 Continued operation increases the engine temperature, causing the engine to completely shut down. Your steering and braking effort increases in this situation.

When the engine temperature cools, you can re-start the engine. Have your vehicle checked as soon as possible to minimize engine damage.

Your vehicle has limited engine power when in the fail-safe mode, drive your vehicle with caution. Your vehicle does not maintain high-speed operation and the engine may operate poorly.

 Remember that the engine is capable of shutting down to prevent engine damage. In this situation:

If you tow a trailer with your vehicle, the engine may temporarily reach a higher temperature during severe operating conditions, for example ascending a long or steep grade in high ambient temperatures.

At this time, you may notice the coolant temperature gauge moves toward the red zone and a message may appear in the information display.

You may notice a reduction in vehicle speed caused by reduced engine power in order to manage the engine coolant temperature.Your vehicle may enter this mode if certain high-temperature and high-load conditions take place.The amount of speed reduction depends on vehicle loading, grade and ambient temperature.If this occurs, there is no need to pull off the road.You can continue to drive your vehicle.

The air conditioning may turn on and off during severe operating conditions to protect the engine from overheating. When the coolant temperature decreases to the normal operating temperature, the air conditioning turns on.

If the coolant temperature gauge moves fully into the red zone, or if the coolant temperature warning or service engine soon messages appear in your information display, do the following: