I believe if you leave the serpentine belt on, place an adjustable wrench on the fan nut and tap/bang counter clock wise, it will release. I saw a video for replacing a water pump and thet's what they did.
2004 Jeep Grand Cherokee Limited 2x4 4.0L
2002 Jeep Grand Cherokee Sport 2x4 4.0L
1998 Jeep Grand Cherokee Laredo 2x4 4.0L
"Three daughters, three Jeeps"