Yet Another Idle Heating Issue

I am sure you guys are getting sick of these posts/issues, and I did a good amount of searching and some relevant tests (though some were unclear what to look for) I am taking the truck out to the desert monday and its getting pretty hot so I want to bust this issue (of course I work 12 hours saturday and sunday so only simple solutions will work)

This all started suddenly tonight, after helping a freind tow his new trailer. While towing I noticed I was running hoter than normal, I usually sit around 195-200, and once I was towing the trailer home I was up to 210-220 on the freeway. Then after letting the truck sit for quite a while when driving around on the street I noticed it was getting pretty damn hot even with out the added loads.

Typical Issue, over heating while at an idle. I have a 95 Sport with open cooling system, 4.0L engine. I bought the truck a bit over a year ago, and have not touched any components on the system up to this point, so I am not sure what is stock and what has been replaced in the 140k miles on it.

Things I have checked.

Clutch Fan - I got the engine nice and hot and when I try to spin the blade it barely moves 1 blade over. When cool I can get it to do about a 1/4 turn. I reved the engine once it was heated up and there was no difference in the cooling power of the fan, weather I was at 1500rpm or 2500+rpm This leads me to beleive my Clutch Fan is working fine and doing its job, so the issue must lie somewhere else.

Heating - I have run the heat and it will come out quite hot, and cool the engine down pretty quickly

Aux Fan - This is working fine, once it kicks in the temp drops pretty fast. Aux Fan + Heat = really quick cool down to normal temps.

Coolant - When I first noticed the issue I checked inside and the coolant was at the add level and looked a bit dirty. I bought some 50/50 at the gas station I was stopped at and filled it up to the full mark, while the engine was still hot (I will check tommorow when the engine is cold to see where its at) Im hoping I didnt have it low enough to suck air into the system and its having an issue burping its self.

From what I have been able to find this leads me to think its one of the following issues.

1. Radiator Cap has gone south and isnt burping the system so I have air in it now.

2. Water Pump is dying and cant move fluid well enough.

3. Radiator has crap in it/needs to be replaced.

Of these things (I may be missing some other options) Im not sure which ones would suddenly manifest them selves in a matter of hours. Im not sure if this could be a t-stat issue either.

So any help diagnosing the issues would be appriciated!

I'm not much of a mechanic but If the water pump hasn't been replaced in your XJ it's probably getting to be that time. I have a 98 and the pump went out without much warning. There was no noise or leaks what clued me in was when the heat started building suddenly on the highway then pressure popped a hose and that was it. Better get it checked. I've had a bunch of 60's era chevys and the water pumps are real forgiving but a cherokee won't leak or make a grinding noise like those old cars do. I had to get mine fixed at a shop cause i had to have it fixed then and there. You could save hundreds doing it yourself at a convenient time. I only have the one experience so factor that in your decision on what to do. Good Luck

Yeah money isnt a huge option right now since I just spent 500 on new rims and a full size spare, then had to do an emergency track bar swap which ran me 300 in the end since my old rustys bar snapped while parallel parking. Im pretty sure I could do it my self, but I just don't have a lot of time before I go out.

honestly, if the pump isn't actually leaking and the jeep isn't massively overheating, the pump is probably circulating coolant just fine. and assuming the fan clutch is in decent shape, at 140k if the po didn't already do it, i would think you're probably due for a radiator. you mentioned the coolant looked dirty, might have a bunch of crap in the tubes....

The radiator just doesnt sound like the main culprit for a sudden change in ability to cool like that, to me at least. I know weird stuff happens in these trucks. I am going to go get the radiator flushed today, hopefully that will help.

i was thinking along the lines of maybe a big wad of crud came loose and wedged itself somewhere? a good flush should help....good luck!

Check for a vacuum leak.

not to sound to stupid, but how do you check for a vacume leak?

Ok, well i got the truck to work today, let it cool down and went out and checked stuff on my break, replaced the radiator cap and made sure everything else was ok. Thromostat works fine, the upper radiator hose works great, gets nice and hot. And I checked the clutchfan again.

Well seems like even when something seemed fine, always double check it. The clutch fan while not exhibiting standard symptoms deffinatly is not working correctly. The clutch seems to have jammed mid position. When cold its stiff and won't free spin, and when hot its about the same though I think even a little less stiff.

So going to replace that on my dinner break and hopefully that will do it!

Feeling stupid, :looser:

Mongo

Issue seems to be fixed, new fan clutch and its cooling its self down at idle just fine.