2001 jeep grand cherokee, 6 cylinder air conditioner will not cool

Could be a blend door problem under the dash.

Jeep Grand Cherokee is notorious for broken blend-air doors. This is the door inside the A/C-heater housing that switches the air from hot to cold. You must remove the dash to repair it.

Check the pressures on the AC system to detemine if it is properly charged. Also make sure the condensor is clean so air will flow freely through it.

If you have the 4.0L six cylinder those run hot. 210-220 degrees. If the cooling system is fine, both fans are working and it's not overheating you can try adding a bottle of "Water Wetter" to the coolant. I also changed my radiator cap to an 18psi which seemed to help run slightly cooler. You find it at the autoparts store.

All you need to do on those is on level ground, run it with the heater on high heat with the radiator cap open. Fill as necessary 'till no more can be added, close it up and add vcoolant to the full line on the overflow tank.
If you are consistently encountering an overheat and finding air in the system you may have a head gasket or cracked cylinder head that is permitting combustion gasses in there. (a hydrocarbon test at the radiator will tell you that).
If you are having any other problem there, ask and I'll try to help.

YEP SOME JEEP 6 CYLINDER ENGINE BELT TENSIONER NOT AUTOMATIC.YOU HAD TO ADJUST BELT TENSION BY LOOSEN THE POWER STEERING PUMP BOLTS AND TURN THE TENSIONER ADJUSTING BOLT TO TIGHTEN OR LOOSEN THE DRIVE BELT.IF YOU HAVE THE AUTOMATIC BELT TENSIONER.EITHER YOU ARE GETTING THE WRONG ONE OR BELT TOO BIG.IF IT WAS ME TAKE TO ANOTHER GARAGE.

Plug, plug wire, plugged or open fuel injector. are the most likely.

While your hood is open and engine running can you hear the air conditioner compressor kick on and off as the engines idleing. Check the fuse for the ac unit. And worst case it could be your compressor witch can be pretty spendy.

If the air blows normally but warm, then you need to check the compressor and its gas. you might have a leakage.

Check the cylinders Commpression. over 115 psi is good, 120 psi is normal.