RUNNING HOT AT IDLE

1996 4.0 AW4 w/ 171,000. Ok I changed out the idiot light cluster so now I know my temp. It runs above 210 always. Recently when sitting at idle for more then a couple minutes it gets almost to the red, but not quite, then when I drive again it goes right back down to a little past 210.

It had a brand new radiator about 1000 miles before I got it, no electric cooling fan, I put a used one in.

My 94 used to run below 210 at all times with no electric fan even in mid summer while off-road.

Should I just try flushing it out and refilling, or could it be something more. I remember when I put the elec. fan in it didn't spin as freely as I thought it should, but ive watched it turn on and it seems to be fine. any ideas? thanks

Two possible issues:

1. viscous clutch fan failing
2. electric auxiliary fan not operating properly

possibly a worn water pump not flowing at idle.

i had same issue last summer and a new VC fan solved it. The old one was shot when I took it off

Gets hot while sitting still, but cools off when you get moving, is the classic symptom of a failed fan clutch. Start there.

i have the same vehicle - had the same problem and turned out to be the auxilary fan..