Runs hot with AC on -
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post #1 of 8 Old 07-19-2011, 08:27 AM Thread Starter
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1995 ZJ 
Join Date: Mar 2011
Location: Waukesha
Posts: 33
Runs hot with AC on

Well the last 2 weeks here in Wisconsin summer has finally come and with these 80-90+ degree days AC is a must for me. I've never had a problem before with my jeep running hot, never goes over 210 degrees. Now after having my jeep running with the AC on after about 10 minutes the temperatures start to go over 210. It gone as high as 230-235 before I'll shut off the AC and then it will start to cool down again. Any idea what would be causing this. My jeep doesn't leak or go through any coolant. At freeway speeds I can leave the AC on and it will stay at about 210 so I'm guessing its an air flow problem. I'm guessing that pointless mechanical fan is part to blame? Electric fans work so much better.

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post #2 of 8 Old 07-19-2011, 08:35 AM
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1995 ZJ 
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Location: New Mexico
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Probably fan clutch since highway speeds are ok.

The lower radiator hose can collapse.
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post #3 of 8 Old 07-19-2011, 08:43 AM
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1993 ZJ 
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i am having a similar issue but its normally when i sit in traffic for 5 mins or so (with or without ac on). the needle slowly increases beyond 210 but with ac on a tad faster. when i start to drive, the temps would decrease slightly and normalize above the 1/4 mark.

I have replaced the water pump, radiator, and thermo two years ago. Did a semi radiator flush (upper/lower rad hoses blew), changed fan clutch 3k mi ago, cleaned the radiator as well as the condenser. does not use oil or coolant.

I thought about going electric as that would definitely cool in slow to stopped traffic. but i want to be sure nothing else is wrong before spending the $$$

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post #4 of 8 Old 07-19-2011, 08:49 AM Thread Starter
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Originally Posted by HighLonesome View Post
Probably fan clutch since highway speeds are ok.

The lower radiator hose can collapse.
What is all involved with changing the fan clutch, is this an easy job? Do they sell the parts at napa or autozone or is that a dealer only part. I've never owned a vehicle with a mechanical fan before, all my previous vehicles had electric fans.

What do you mean by the lower radiator hose can collapse?
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post #5 of 8 Old 07-19-2011, 09:17 AM
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The engine pushes water out of the top hose, into the radiator, returning thru the bottom hose. Meaning the bottom hose is the closest to suction in the system. Factory puts a thing that looks like a stretched out slinky inside the hose to prevent collapse. Cheap hoses do not have the spring, and people forget to transfer them across. Certain conditions the hose will collapse and stop water flow. Instant overheat.

Fan clutch is a standard parts store item. Look at your fan, it's the silver thing that the blades bolt to. It allows the fan to slip when the engine is cold because the fan eats like 10hp. When hot the clutch locks up for maximum airflow.

Inside the fan clutch is silicone fluid. Normal failure mode is to leak that fluid out, and it's sticky. The #1 sign of a failing clutch fan is sticky residue around it's seal. All other engine grime is oily.

Electric fans have some advantages, but when converting the main concern is finding an electric that can move as much air as a mechanical. When the engine is revved up and hot, like a truck working under load, an electric can't compete with the air movement of mechanical. When sitting at a stoplight, the mechanical can't compete with the air movement of an electric.

You can also troubleshoot your clutch fan by locking it in with baling wire between the water pump and fan bolts. Or avoid buying a new clutch for an old beater that's only gonna live a few months anyway.

good luck
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post #6 of 8 Old 07-19-2011, 11:58 AM
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1997 ZJ 
Join Date: Feb 2008
Location: Hudson
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Mine did the same thing last year. It was the fan clutch. Not terrible to change, basically need a 36mm wrench (i think) for the nut that holds the fan assembly to the pulley on the motor and something to jam the pulley while you loosen the nut, you also need to take the fan and fan shroud out together and put them back in together because of space constraints. I bought a heavy duty one and if you can find a normal duty one buy it. With mine, the clutch never disengages the fan except for when its below freezing out. It robs a ton of horsepower you can actually feel.

Current jeeps:
1997 ZJ Orvis
1997 TJ 4.0L 5-speed
1993 YJ Sahara Trail Rig
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post #7 of 8 Old 07-19-2011, 12:51 PM
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1995 ZJ 
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I would avoid the Auto Zone fan clutch. I bought one a year ago, and it is already time to replace it. Gonna spend the extra $10 and get a Napa max cooling fan clutch this time.

1995 ZJ 5.2L V8 318. 230,000 miles and still rollin.

List of parts not replaced yet:
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post #8 of 8 Old 07-19-2011, 04:34 PM
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I did the taurus fan swap because I would overheat at low speed with the mechanical fan when the ac was turned on.
Since I almost never tow anything, it works well for me and what I do with my jeep.

Moss Green 95 5.2l ZJ- 5.5" IRO lift, 255 75 R17 BFG M/T on JK Moabs, Mopar ECU, Mopar Tire Carrier
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