In 1984, Jeep released an all-new compact SUV: the Cherokee. Prior to 1984, Jeep used the Cherokee name as the sporty trim level of the Wagoneer.
The 1985 Cherokee had three engines available: a 2.1-liter four-cylinder, a 2.5-liter four-cylinder, and a 2.8-liter V-6. All three engines use similar cooling systems and can develop similar problems.
Cooling Fan Problems
The 1985 Jeep Cherokee uses a flex-blade cooling fan to cool down the coolant in the radiator before the fluid reenters the engine. The fan blades on this type of fan flex as the engine’s speed increases, resulting in lowered engine noise and increased engine efficiency.
This pitch change under high rpm also decreases the airflow created by the fan, as the anticipated movement of the SUV supplies sufficient airflow. If the fan becomes distorted from its constantly changing pitch or impact, you may experience overheating.
The fan also has a thermostatic clutch that increases and decreases the fan’s rotational speed with the engine temperature: As the temperature increases, the clutch tightens and the fan rotates faster; as the engine cools, the clutch loosens to slow the fan’s rotation.
The 1985 Cherokee requires a 50-50 mixture of ethylene glycol-based (green) antifreeze and clean water to keep the engine cool. The 2.1-liter diesel engine holds 2-1/4 gallons of coolant; the 2.5-liter engine holds up to 2-1/2 gallons of coolant, and the 2.8-liter six-cylinder engine holds up to 3 gallons of coolant.
When the coolant level is low, it cannot remove heat from the engine at a rate rapid enough to keep the engine within its operating temperature. This will result in the Cherokee’s engine overheating. If the coolant is low, there is likely a leak — internal or external — and you must perform a leak check on the cooling system.
Jeep positioned the 1985 Cherokee’s thermostat on the front of the engine block, just below the valve cover. The thermostat has a valve that opens and closes to regulate the flow of coolant from the radiator to the engine.
The thermostat can fail in three ways: stuck closed, stuck open or showing delayed response. If the thermostat sticks closed, the coolant cannot flow into the engine, resulting in your Cherokee overheating. If the thermostat sticks open, the coolant flows unrestricted through the engine and radiator — this unrestricted flow can result in the SUV over-cooling, which can result in poor engine performance and lack of heat coming from the vents. The final thermostat issue is delayed response. This is when the thermostat does not start opening at 192 degrees F in the four-cylinder engines or 197 degrees F in six-cylinder engines. When this occurs, the engine overheats slightly until the thermostat finally responds by opening up. Once opened, the engine cools off to its correct operating temperature.
Water Pump Failure
The water pump on the 1985 Cherokee is mounted just behind the cooling fan clutch, attached to the front of the engine block. The serpentine belt on the engine turns the water pump pulley and rotates an impeller inside the water pump. This impeller rotation is what pushes the coolant through the cooling system.
Over time, or due to lack of maintenance, the water pump bearing or impeller may fail. This prevents the coolant from flowing through the cooling system, resulting in overheating.
Cooling System Blockage
Jeep recommends draining and refilling the 1985 Cherokee’s cooling system every 3 years or 45,000 miles, whichever comes first. If you do not follow this recommendation, the coolant may congeal and cause blockage in the cooling system. This prevents the coolant from flowing correctly, causing overheating.
The 50-50 mix of antifreeze and coolant in the cooling system helps prevent rust from developing in the system. If you fill the system with just water, it will rust and possibly clog the cooling system, causing overheating.
- AutoZone Repair Guide: 1985 Jeep Cherokee Thermostat
- AutoZone Repair Guide: 1985 Jeep Cherokee Cooling System
- Edmunds.com: Jeep Cherokee History
- “Mitchell1 OnDemand 5”; 1985 Jeep Cherokee Cooling System; The Mitchell Repair Information Company