I'll be damned, if the efan shuts off with a/c off, then the coolant is under 218F, according to the FSM. Your XJ cooling system must be in tip-top condition......u and the PO are to be commended. '00-'01 models have temp sensitive efans, previous models are both temp sensitive and a/c on to engauge the efan. I just love those posts that start off saying I'm overheating and have brown clumpy crud in my..............

 

I am not going to get into all the technical jargon running rampant. All I'm saying is that on two of my XJ's (1990 & 1992), I spent a few hundred replacing waterpumps, radiators and thermostats. All failed to keep them from overheating in stop and go traffic. ( No air Circulation through Radiator) One is a closed system and one is an open. The only fix that worked was dropping to a 180*. On my third XJ, it was the first mod I did, and not a problem has surfaced.
All three are running cool in the traffic! There is no noticable change in fuel or performance, maybe if I put a calculator and calipers to it!

 

How would a 180 t-stat have an effect on air circulation thru the rad?

 

It has nothing to do with air circulation, only the temp the water starts circulating through the radiator. My point is the the water quit boiling out when I went to a 180•

 

Sorry, guess I misinterpreted.