2004 Jeep Grand Cherokee Owner's Manual - Page 272

272 MAINTAINING YOUR VEHICLE Cooling System Pressure Cap The cap must be fully tightened to prevent loss of coolant, and to insure that coolant will return to the radiator from the coolant reserve tank. The cap should be inspected and cleaned if there is any accumulation of foreign material on the sealing surfaces. Coolant Level Check the coolant level at least once a month or more often in hot weather. Check the level when the engine is at normal operating temperature. Check the coolant level only in the coolant recovery bottle. The coolant level must be between the FULL and the ADD mark on the bottle. WARNING! The warning words DO NOT OPEN HOT on the cooling system pressure cap are a safety precaution. Never add coolant when the engine is overheated. Do not loosen or remove the cap to cool an overheated engine. Heat causes pressure to build up in the cooling system. To prevent scalding or injury, do not remove the pressure cap while the system is hot or under pressure.