* Cooling System Fan Issues: The most probable cause. The radiator fan is crucial for cooling, especially under high load (like the AC compressor running). Check these:
* Fan Clutch: A failing fan clutch won't engage the fan at the necessary speed, especially when the engine is hot and the AC is on. It should spin freely when cold, but lock up and spin fast when hot.
* Fan Motor (Electric Fan): If your Jeep has an electric fan (some did, some didn't), it might be failing, wired incorrectly, or its control module might be malfunctioning. The fan should turn on when the AC is running and the engine temperature is high.
* Fan Shroud: Ensure the fan shroud is properly installed and intact. It directs airflow through the radiator, making the fan much more efficient.
* Radiator Issues:
* Clogged Radiator: Over time, radiators can become clogged with debris, reducing their cooling capacity. Flush the radiator with a proper cleaning solution.
* Radiator Leaks: Even small leaks can significantly impact cooling performance. Carefully inspect the radiator for any signs of leaks or damage.
* Water Pump: A failing water pump won't circulate coolant effectively, leading to overheating. Listen for unusual noises (whining, groaning) from the pump.
* Thermostat: A stuck closed thermostat will prevent coolant from circulating until the engine gets extremely hot.
* Coolant Level: Check your coolant level frequently. Low coolant will dramatically impact cooling ability.
* Head Gasket: A blown head gasket allows combustion gases to enter the cooling system, pressurizing it and potentially causing overheating. This is a more severe issue often accompanied by other symptoms like white smoke from the exhaust, milky oil, or loss of coolant.
Troubleshooting Steps:
1. Check Coolant Level: The simplest first step. Top off if necessary, but be careful of hot coolant and pressure.
2. Inspect the Radiator: Look for leaks and check for debris restricting airflow.
3. Test the Cooling Fan(s): Manually check the fan clutch (when hot, it should lock up and spin rapidly) and check the electric fan (if equipped) operation.
4. Check the Thermostat: Ensure it opens at the correct temperature.
5. Inspect the Water Pump: Listen for noises and check for leaks around the pump.
6. Pressure Test the Cooling System: This can reveal leaks not easily visible.
7. Check for Head Gasket Issues: While less likely given the specifics, this should be considered if other issues are ruled out.
If you're not comfortable working on your vehicle's cooling system, it's best to take it to a qualified mechanic for diagnosis and repair. Overheating can cause serious engine damage.
