No need to search, I'll be happy to answer.
The number one reason for an MJ/XJ to overheat is from the radiator becoming partially plugged over time. It can also overheat if the fan clutch is bad, or if the aux fan isn't turning itself on for some reason. Vary rarely the thermostat will stick, but this is easy to detect if the upper radiator hose stays relatively cool.
If these things seem to be working properly, it's time to pull the radiator and either get it rodded out or replace the radiator. The engine driven fan has proven to pull more air, and be more effective, than another electric fan. The electric may have an advantage at slow speeds, but as the RPM's come up they don't match the regular fan.