See Figures 1 and 2
The cooling system was filled at the factory with a high quality coolant solution that is good for year-round operation, which protects the system from freezing. If coolant is needed, a 50/50 mix of ethylene glycol or other suitable antifreeze and water should be used. Alcohol or methanol base coolants are specifically not recommended. Antifreeze solution should be used all year, even in summer, to prevent rust and to take advantage of the solution's higher boiling point compared to plain water. This is imperative on air conditioned models; the heater core can freeze if it isn't protected.
See Figures 3 and 4
The coolant should be checked at each fuel stop, to prevent the possibility of overheating and serious engine damage. To check the coolant level simply look into the expansion tank.
If the level is low, simply add coolant mixture to the tank until the upper level line is reached. If the system shows signs of overheating and, possibly, a small leak, you may want to check the level in the radiator when the engine is cold .
Each year, the cooling system should be serviced as follows:
- Wash the radiator cap and filler neck with clean water.
- Check the coolant for proper level and freeze protection.
- Pressure test the cooling system using a cooling system pressure tester and follow the tool manufacturers instructions. If a replacement cap is installed, be sure that it conforms to the original specifications.
- Tighten the hose clamps and inspect all hoses. Replace hoses that are swollen, cracked or otherwise deteriorated.
- Clean the frontal area of the radiator core, and the air conditioning condenser, if so equipped.
DRAIN & REFILL
See Figures 5, 6 and 7
Every 3 years or 45,000 miles (72,000 km) whichever comes first, the system should be serviced as follows:
- On Cherokee, Comanche and Wagoneer models, remove the front grille assembly.
- With the engine turned off and sufficiently cooled down, remove the radiator cap.
Place a drain pan underneath the radiator, then open the draincock which is found in the following locations:
4- and 6-cylinder engines-right, lower side of the radiator
If necessary, remove the cylinder block drain plug(s), found in the following locations:
4- and 6-cylinder engines-lower left side of the engine block
- Completely drain the coolant, close the draincock and install/tighten the drain plug(s), if removed.
- Add sufficient coolant to provide the required freezing and corrosion protection (at least a 50% solution of antifreeze and water). Fill the radiator to the top and install the radiator cap. Fill the reserve/overflow tank to the FULL cold level.
- Place the heater control unit in the HEAT position and run the engine with the radiator cap in place.
- After the engine reaches normal operating temperature, turn the engine off and allow it to cool. While the engine is cooling down, coolant will be drawn into the radiator from the reserve/overflow tank.
- Add coolant to the reserve/overflow tank as necessary.
Only add coolant to the reserve/overflow tank when the engine is cold. Coolant level in a warm engine will be higher due to thermal expansion.
- To purge the cooling system of all air, the heat up/cool down cycle (adding coolant to a cold engine) must be performed 3 times. Add the necessary amount of coolant to raise the level in the reserve/overflow tank to the FULL mark after each cool down period.
FLUSHING & CLEANING THE SYSTEM
A well maintained system should never require aggressive flushing or cleaning. However, you may find that you (or a previous owner) have neglected to change the antifreeze often enough to fully protect the system. It may have obviously accumulated rust inside, or there may be visible clogging of the radiator tubes.
There are two basic means of rectifying this situation for the do-it-yourselfer. One is to purchase a kit designed to allow you to reverse-flush the system with the pressure available from a garden hose. This kit comes with special fittings which allow you to force water downward inside the engine block and upward (or in reverse of normal flow) in the radiator. The kit will have complete instructions.
The other means is to purchase a chemical cleaner. The cleaner is installed after the system is flushed and filled with fresh water, and cleans the system as you drive a short distance or idle the engine hot. In all cases, the cleaner must be flushed completely from the system after use. In some cases, it may be necessary to follow up with the use of a neutralizer. Make sure to follow the instructions very carefully. These cleaners are quite potent, chemically, and work very well; because of that fact, you must be careful to flush and, if necessary, neutralize the effect of the cleaner to keep it from damaging your cooling system.
If the radiator is severely clogged, it may be necessary to have the tubes rodded out by a professional radiator repair shop. In this case, the radiator must be removed and taken to the shop for this highly specialized work. You can save money on the job by removing and replacing the radiator yourself, as described in Engine & Engine Rebuilding .