Upgrading Factory Cooling System on Jeep Cherokee XJ 4.0L

Third, address airflow. The factory mechanical fan clutch wears out over time, reducing its ability to pull air through the radiator. Installing a heavy-duty ZJ fan clutch (from a Grand Cherokee) increases fan speed to 70-90% of pulley speed compared to the stock unit’s 60-70%, creating that distinctive “airplane taking off” sound that tells you cooling is happening . Many owners also upgrade the auxiliary electric fan to a later-model 10-blade curved design from 1997-2001 XJs, which moves significantly more air than early 6-blade versions . For serious off-road use, the Mishimoto triple electric fan system replaces both factory fans with three 950 CFM units, boosting idle airflow by nearly 42% .
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