Overheating

[Paul Hittie]

New radiator and thermostat last year.  Started overheating at idle at the Memorial Day parade.  As soon as I start  moving, everything goes back to normal operating temp.  On the road, on the freeway runs at normal temp.  Swapped out the fan clutch today, should have done it last summer when I did the radiator.  No improvement.  Plenty of coolant, right at the full mark.  My brain says it is not acting like a water pump or thermostat, my gut says I should swap them out anyways.  Am I missing something?

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[Ken]

Did you put a NEW fan clutch on it.  That is what it sounds like to me.  Could be a loose fan belt. My truck has a fan clutch that is turned on electrically with a temp switch.  It that how it works on your Jeep?  If so check the wires.

[Paul Hittie]

Fan clutch was brand new out of the box, it was purchased last year when I swapped the radiator, didn't realize I forgot it until after everything was back together.

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[Ken]

It could be the water pump, but the impeller would have to be worn a lot, or broken.

[alan6271]

Is it losing coolant at all?

One of the things I wonder, even though the radiator is new as of last year, you have wheeled it and it's possible the radiator fins are plugged.  Did you inspect them with a flashlight to make sure they are clear?

[alan6271]

One more thing does come to mind.  If you let it idle with the radiator cap off does it look like it's circulating good?

Also, you might want to burp it.  There may be air trapped in the system that won't let the fluid pass through at idle.

[Paul Hittie]

I will give those a look-see Alan to make sure, it really has to be something simple like that that I am overlooking. 

[alan6271]

Thats what I'm thinking too.

[Paul Hittie]

For those that have known me for less than 40 years, my first nickname was given to me by my mother - "Prof" was because I reminded her of The Absent Minded Professor...smarter than most people but lacking in common sense in a painful way.

Somebody with more wisdom than I would have checked the fluid level in the radiator first, and not assumed that because the overflow bottle was happy the radiator was full.  We will replace the radiator cap in the morning for good measure but it sat idling in the drive tonight for over 10 minutes, cool as a cucumber.  Tomorrow will be hot, I will retest tomorrow in the heat of the day.  Thanks for your input everbody.

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[alan6271]

Dang it.  I almost typed that too but thought "Nah, that's like asking if the computer is plugged in"