OK, I've researched and I'm still stuck! Here is the story:

My '93 Cherokee always ran @ 210 degrees; but if I was stuck in traffic, it would creep up a bit. Electric fan never kicked on, viscous fan works fine (spins freely when cold, tightens when warm.) I decide it must be a sensor after I connect the fan to the battery and it comes right on, so I decide to replace the sensor. I end up replacing both the temp sending unit on the back of the 4.0 head (for the gauge) as well as the sending unit for the PCM on the thermostat housing, and NOW the temp gauge runs a LOT hotter than it ever did, about half-way between 210 and the red zone. It fluctuates a lot, even at highway speeds, and the fan will occasionally kick on now. My infra-red sensor shows 215 - 225 when I aim it at the T-stat housing.

So basically, I "broke" my XJ and made it run hotter.

I have tried to "burp" the system (do you even need to do this on a '93?) multiple times, put back the front sending unit (the rear sending unit for the gauge is the new one, as I broke the old one getting it off) and it still runs much hotter than before. Coolant is fairly new and clean, but I am thinking about taking it down to my mechanic and having them flush it and start all over. I hate spending the money, but I am running out of options.

Any ideas? I wanna get this squared away before it gets really hot and leaves me stranded...

 

replace the thermostat?

 

Hi, you can try flushing it out yourself (I did mine and it runs a lot cooler) with the "Prestone Flush Kit" for around $4. It will back flush the entire system from your heater core to your engine...Tj

 

if you try the flush and that doesnt work then you can get a rad from ebay for about 70 bucks and it fits perfect as stock and is actually really nice, also while you are in there i would go ahead and replace the water pump its much easier when the rad isnt there as i found out the hard way basically you are replacing your entire cooling system but for around 100 bucks for new cooling sytem its not that bad. trust me on this on i just did it on my 93 and also i did burp the system and used the flush kit that trekker recommends. its worth the dough cause mine runs great now it only has gotten to 210 while offroading and that was on like a 70 foot winch pull with her reving up so i didnt kill the battery.

 

Thanks guys... I am gonna try to flush it out later this week, and see what that does. If no improvement there, then I will probably replace radiator, water pump, hoses, etc... Might as well go "all in", huh?

I just hate mucking with something that was fine and making it worse... <sigh>