Yea, I'm also going to chime in here.
I had some major cold-running problems....The factory gauge would read less than 160 freeway, 90* + outside temp. Now, with a new dealer t-stat, new upper/lower rad lines, and a flushed heater core, things had seemed to have smoothed out a bit.
With the colder temps coming in, I've noticed that my gauge will come close to 210 upon warm-up, then will drop back down to 160-175*. A leaking pressure cap was suggested....is it possible that this could also be caused by a leaking heater hose?? Seems that somehow mine got jacked up during my heater core flushing......it appears to be leaking out of the lower hose, directly from the firewall...
Any ideas would be great, as I've noticed my MPGs dropped off sharply recently. I attributed it to the winter fuel, but it could also have something to do with the leaking/broken exhaust manifold.....
89 XJ, Renix 4.0L