Temp creep thenRough idle when in long traffic jams

[solomon7]

Aside from the strange rattling I've been hearing on light throttle, today my 96 auto, after about 30 minutes in bad stop n go traffic temps stared to creep up over the usual 195-200 to around 220.
Just past 210 idle got rough and almost bucky.
It did this the last time I was moving slow in a traffic jam for about 30 minutes last week. Both times outside temps weren't over 65.
I have a Nice CSF radiator and ZJ fan clutch on it , but the clutch is about 6+ yrs old.
I had the belt too tight after doing a water pump and thermosat 4 months ago, so I took it off and checked things for damage.
The water pump when spun by hand made a faint groan now but no wobble or in out play so I properly tensioned the belt.

I'm wondering:
Could my fan clutch be going out and that's the rattle/squeal I've heard faintly lately and possibly the temp creep? It seems not as loud as it used to be fwiw.
Also, would that tiny bit of groan mean the water pump's shot?

Still doesn't explain why my idle is crap when hot though.
THoughts?

 

[ThePnsh3r]

Are you losing coolant by any chance?

 

[solomon7]

Not a single drop.

 

[ThePnsh3r]

Have you made sure that there is no trapped air in your cooling system? I've had something similar happen once and after I burped it then temps came down. Another common issue is collapsed coolant hose. Those are more likely to manifest themselves when temps come up as the rubber gets softer. While under hood, engine temp at operating, without getting your hand chopped off - inspect all coolant hoses, and particularly at elbows. You could rev the engine a bit and keep an eye on lower coolant hoses. Hope this helps

 

[McQue]

Your electric fan should kick in when in heavy traffic and temp goes up... Is it turning on? Mine was having trouble starting up intermittently ... replaced it... all set.

 

[JeepNoob]

Mechanical fan shroud all in one piece and installed? If not, fix that first. If you suspect your fan clutch is faulty, when the problem occurs, pull into the nearest gas station and pop the hood. If you're really worried about it, I guess you could just idle it at home. Let the engine get up to operating temp (middle of dash temp gauge) and then let it run (run, not drive) for another 10 or 15 minutes. Shut the engine off and while trying not to burn yourself, try turning the fan by the blades. Any movement would indicate a bad fan clutch. No movement (like, you feel like you're gonna turn the whole engine and all the accessories if you try turning it any more) indicates a good fan clutch. Had a similar problem maybe a year or so ago. I don't think the fan clutch was bad, just that the coils in the front were full of grime and couldn't expand/contract and do their job. I replaced it anyways, and no problems since.