92 XJ overheating

[The Butcher]

I got a 92 XJ with the 4.0, and the engine keeps getting hot. It usually gets up to about 250 and stays there, cools a bit when Im driving and gets hotter when Im at idle. Im going to change the thermostat, hopefuly thats the only problem, but I dont think so.
The coolant tank was low so I topped it up, and afew days later is started to get low again.
I was hoping you guy's could give me some suggestions on what the problem could be. Im hopping anyhting other than the head gasket.
The rad is original, and kinda beaten up. So that is going to replace that as well for sure.

 

[SteelHeadz]

Are both of the radiator fans working?.

 

[MudderChuck]

When it starts overheating at idle it is usually a weak fan clutch.
If the coolant is missing from the canister it is going somewhere, sometimes the leak is so small the coolant will evaporate before it gets to the ground. Common spots are the lower radiator hose where it connects to the water pump, the front of the water pump itself or sometimes upper right on the radiator inside behind the fan shroud. If it has been leaking for awhile it will usually leave a white stain or a stain tinted the same color as your coolant someplace or even a powdery buildup.
If the coolant is leaking out, during cool down periods when the motor is shut off, it may suck some air back into the system. Which also degrades the coolant flow, air pockets are not good.
Like mentioned check to see if the electric aux fan is coming on when the temperature gets higher than normal. Mine usually kicks on when the temp is near 230, but this can be lind of subjective. The temperature gage is known to have a rather large error margin on occasion.

 

[The Butcher]

Sorry, I made a mistake, it doesnt run at 250, probably around 220 to 230.
The electric fan does kick in, I can hear it running, but in doesnt really bring the temp down. On one occasion it did get up to 250 while I was sitting. It has to be leasking somewhere, but theres never been and fluid on the ground, and I havent seen and dried up coolant around the engine.
What is the average temp this engine should be running at? I'll check inside the fan shroud today, and the lower hose.
I've read somewhere that the electric fan can short or something, to make it reverse flow, and be useless. If this is the problem, how do I fix that? Also, I've heard about open and closed systems? What are those and how do i figure out what do I have?
Thanks for your reply's so far.

 

[SteelHeadz]

The thermostat should open above 195 degrees. The average temperature on a XJ 4.0 is around 210-220. If your loosing coolant not from a boil out and or external leaks, you need to get the system pressure tested and start looking for signs of internal leaks. The electric fan module is a two wire system. There is no way it could reverse its rotation unless you physically reverse the wire connections on the fan module. Either they work or they dont. Make sure the clutch fan is also working properly when the engine is at normal operating temperature. Both the mechanical and electrical fans works together to maintain the engine temperature from the information gathered from the engine coolant sensor.