I have a 99 cherokee sport with a 4.0 with no heat. The jeep was sitting for about three months. I put in a new thermostat with no luck. I flushed out the heater core and got some heat but not burning hot. I did notice that the radiator cap did not get burning hot either, so I just replaced it. Someone told me to check the fan clutch because it is overcooling and some kind of blockage would cause an overheat not an overcool. The temp gauge does move, but past 130 and according to the guage never reaches operating temp. Any ideas or suggestion would be great because its getting cold here.

 

i know when i bought my 97 i had very little heat so i back flushed the heater core by hooking the garden hose to the return line of the heater core and had a bunch of crap come out of it now it cooks me also try this with your radiator but leave your cap on so it pushes all the crap out but not sure if this will work for ya but it cant hurt