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Unread 07-03-2006, 05:47 PM   #1
Kcolg
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ZJ overheats with AC on?

Whenever I turn on the AC within a few minutes the temp guage goes to about 240 degrees, even if I am traveling 70 on the highway. If I turn it off, the temp guage will go back down to my normal 210. I am not sure if it would ever reach the 260 red line as I always turn it off once it get to about the 230-240 mark.

Coolant level is all good, and I just did a flush about 3 weeks ago. My thought was the thermostat, but I do not see why the AC would be the only thing to effect it. Any thoughts?

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Unread 07-04-2006, 01:38 AM   #2
PDshooter
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1.Could be your cluch fan ?
2. How old is your Rad, ?
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Unread 07-04-2006, 04:36 AM   #3
Turbonut
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Quote:
Originally Posted by PDshooter
1.Could be your cluch fan ?
2. How old is your Rad, ?
I'd suspect the radiator first, as if you're doing 70 mph and the temp won't come down, I'd think the radiator can't remove the heat because of the restriction. Fluid could look clean but radiator still could be clogged. Normally if the clutch goes, it won't cool in heavy traffic as there won't be enough air being pulled across the radiator.
Check both out, and although very remote, check to be certain the lower radiator hose isn't collapsed when hot.
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Unread 07-04-2006, 10:02 AM   #4
PDshooter
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I'd suspect the radiator first............You bet, me too!
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Unread 07-04-2006, 10:07 AM   #5
GreenDean
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Change your thermostat.
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Unread 07-04-2006, 02:14 PM   #6
jeep946
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chang the rad cap if it is bad the cooling system will not build any pressure and inturn under a load it will overheat.
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Unread 07-04-2006, 02:41 PM   #7
wmchurch
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Yeah, radiator cap is a high underrated fix. Remember if there is no pressure in the system the boil point lowers, the higher the pressure the higher the boil point. It's the easiest thing the try, and is under $10. And, if there is no pressure, when it does finally boil most will escape the system as steam. An 18lbs cap raises the boiling point to 222 deg F instead of 212 (this really varies with altitude and barometric pressure though).

I've always seen the radiators leak on Jeeps before they clogged, maybe it's just me though.

Fan clutch, your issue would be at idle and low speeds mostly. Thermostat, could be any time, but a weak spring will cause it to close under pressure, so that's a high possibility as well. Another cheap fix too.

The radiator return hose (lower) is known to collapse at times under load. I think if you can easily squeeze it together, it should be replaced. The good ones have a spring inside to prevent this, if you do get a new one make sure it has the spring. However, with your symptoms I don't know if that fits.
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Unread 07-04-2006, 06:02 PM   #8
Kcolg
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Thanks for the input.

The radiator was replaced about 2 years ago.

The temp will come down on its own and back to normal, if I turn the AC back off. Did some searching on here and checked the fan to see if it was too stiff or too easy to turn to indicate clutch and bearing issues and it appears to be okay as well. If I give it a spin it seems to turn about 1/2 to 3/4 of a turn as if spinning in molasses as it was described in other posts.

Never had the radiator cap boil over, but may replace it first to see what happens. I also bought a new thermostat today, I do not ever remeber replacing it since I have had the vehilce - 1999.

Will also check lower hose for wall rigidness.

Thanks again.
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Unread 07-04-2006, 06:05 PM   #9
Virmagicus
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If the hose is soft you can use a zip tie to make it somewhat round again to see if it will help .
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Unread 07-05-2006, 09:51 AM   #10
Kcolg
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Well I got the issue fixed and feel stupid after talking to a "kid" at Autozone last night.

I went back to buy a new radiator cap just in case that was my issue, even though I had never seen any signs of it leaking. Figured it was only $6.

Anyway while checking out I mentioned my overheating symptoms and he said, "Have you cleaned out the AC condesor?" I told him no and asked how do you mean clean it out? He said just take off your front grill and use a power washer to spray it off.

So I go home and hooked up the power washer, took the front grill off, and it looked okay but went ahead and sprayed the thing down. Started up the Jeep and let it run with AC on high for 20 minutes and not only did the temp not raise, my overall running temp lowerd by 10 degrees to about 195-200.

Heads up to others with this issue or any overheat issue, try cleaning the fins, even if they already appear clean.

Lesson, don't always just throw parts and money at the problem, go ask some kid at Autozone what he would do.

Got to love a FREE fix.
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Unread 07-05-2006, 09:53 AM   #11
wmchurch
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Not only do you feel stupid, but I feel stupid too. I should have mentioned that, it's something I always forget. It's the first thing you see in almost any troubleshooting procedure that has to do with overheating. Funny how a few bugs can ruin your day.



Good to hear, nothing better than a free fix!
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