X2 on the water pump . Sounds like the engine coolant is lost under pressure which may be the water pump. Whether you have the 4.0 liter six cylinder or the 4.7 liter V8 , the leak inspection will be similar . See if the front of the engine is wet or if you see coolant dripping from the water pump . Don't exclude things like hoses , radiator , overflow reserve tank or even the heater core. Are the Windows fogging even a little and is there a scent of coolant inside the cabin ? It will be a somewhat sweet smell but noticeable. You can try to loan a pressure tester from autozone if you live near one . With the engine off and cold ( no pressure ) you just remove the radiator cap and put on the tester and pump some pressure into the radiator/cooling system . Wherever the leak(s) is/are , the pressure will force out the coolant and your leak is found. Also , have you noticed any coolant dripping from the firewall area from the moisture drain for condensation from the air conditioning beside the water that normally drips from there ? If coolant is found to be dripping from there , the heater core is leaking . Be sure it's not a heater core hose connection that is leaking. Be sure the connections are not leaking and are tight . Use care when handling hoses on heater core connections under the hood since on some vehicles the heater core has plastic tubes and plastic tanks that the hoses attach to. Rough handling can cause cracks and on down the line , leaks. A heater core swap in a WJ is an expensive job since it entails much disassembly . You'll want to inspect to,the best of your ability before a mechanic gets their hands on it and spends all your vacation money for you. Wishing you the best . There are you tube videos on the heater core swap if your interested.
