See I don't get it. I have a new water pump and clutch fan with a toggle switch for my stock electric fan and my XJ runs at 210 all day. Never gets cooler. I don't want to rob more power away from the engine than is needed so an even more taxing fan clutch is out of the question for me.

My beef is that I've read several times that just changing the thermostat to a cooler one not only doesn't make any fdifference, but can also screw with the computer somehow in my 1998. Anyone else hear this? So I'm stuck with installing a larger rad and/or dual electric fans. How Tue hell is my XJ running so hot here in the East coast of Virginia? Its 60 degrees outside mid day and it still wants to run over 210 at a stop, idling for more than 10 minutes.

You have a fan shroud on there?

Have you done a full system flush? Sounds like some maintenance is in order. 210 is pretty normal for XJ's though. As far as the thermostat, you could install a 180 or 195, but nothing lower. It will not affect your gas mileage or computer settings, this is a popular myth out on the internet.

I went on line to Napa with the 272310 p/n and this is what it said:
P/N 272310 w/ Heavy Duty Fan Clutch,w/ Reverse Rotation Fan Clutch.

Someone said "make sure it's the ZJ clutch WITHOUT HD cooling"

So I am confused about that and should it be Reverse Rotation?

I live in southern MD and work in Northern VA so familiar with climate. Until recently I was running temps like you report. New water pump, rad, heater core and tstat and now stay under 210 consistently. Stock fan clutch and elec fan 291k miles. Rad tstat and water pump were done before heater core with under 210 temps. Also use good ole green antifreeze and distilled water somewhere close to 50/50 mix.

Spectra rad and heater core, new napa water pump and tstat.

Not sure what they were talking about. 272310 is the one I got from NAPA. I'm actually looking to get rid of it now because my rig has been cool and with winter coming, it's not worth the loss in horsepower.

I know this thread is older but for newer XJs running 210 is the correct operating temp from factory.

Pretty much.