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Bad fan clutch?

12K views 8 replies 7 participants last post by  GringoLoco 
#1 ·
2002 TJ 4.0L
157k Miles

Things I have replaced within the past 6 months:
Thermostat & Housing
Radiator Cap
Radiator
Radiator Full Flush

I spent the past week at silver lake sand dunes here in MI and all went well the entire trip until the last day. I noticed that when at idle or low speeds the temp needle will spike to about 220 or so. Before the dunes, she wasnt having any overheating issues at all.

Today when I drove to work on the freeway for work 25 miles it didnt spike over 210 at all. However once I got off the freeway and came to stop lights, it started to jump. I also started to hear a minor squeaking noise coming from under the hood that increased with rpms. When I parked the jeep, I popped the hood and with the engine off and hot, spun the fan with the hand to find that it had little to no resistance and spun freely.

I am assuming it must be the fan clutch but I just want to make sure before I go and replace it. The only two things I havent replaced in the cooling system in the past 3 years I have owned the Jeep is the water pump and the fan clutch.

Also how difficult it is to replace if that ends up being the issue.

Thanks
 
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#2 ·
If the upper tube on the radiator is hot, then the pump and t-stat are working. 220 is not too hot IMO. 210 is normal. You could make sure the belt isn't slipping before you do anything else. The fan is pretty easy to replace. Over 230 would concern me that I had a problem. How hot is it outside?
 
#4 ·
When I parked the jeep, I popped the hood and with the engine off and hot, spun the fan with the hand to find that it had little to no resistance and spun freely.

I am assuming it must be the fan clutch but I just want to make sure before I go and replace it.
From FSM:

DIAGNOSIS AND TESTING
VISCOUS FAN DRIVE
If the fan assembly free-wheels without drag (the fan blades will revolve more than five turns when spun by hand), replace the fan drive. This spin test must be performed when the engine is cool.​

But, I suspect you'll get the same results with a cool engine — looks like a worn fan clutch.

The Fan Clutch is an easy install.
Best bet is to go to AutoZone (or equivalent) and rent (for free) a fan clutch wrench.
The threads are right-handed on 2000-2006 4.0 TJ's. With the wrench on the nut, give the wrench a few taps with a hammer (counterclockwise), and it should come loose (if not, with a breaker-bar or socket wrench on the accessory belt tensioner, tighten the belt, and while tight, tap the wrench again)

Here's a good write-up: http://www.4x4xplor.com/fan-clutch.html
 
#7 · (Edited)
The fan clutch should allow the fan to be turned by hand much easier cold than when the engine is at operating temperature. Where you may get 2 or 3 revolutions spinning by hand when cold, you shouldn't even get one when hot. Screeching can come from an improperly tensioned belt, but it can also come from a bad fan clutch, or even a bad water pump bearing. Fortunately fan clutches are easy to change.

From your description of the symptoms, temp shooting up at lights etc., but cooling down when moving on a 70 degree day, I suspect the fan clutch.
 
#9 ·
Another vote for fan clutch. Cold or hot it shouldn't spin that easily, especially not when hot. It's easy to replace, I was even able to just use a large crescent wrench instead of a serpentine belt tool. If you have a lot of miles on the belt I'd replace it whether it looks good or not. They're cheap and it's good peace of mind. I upgraded mine to the Goodyear Gatorback one, don't know how much of a difference it makes realistically. You'll have instant confirmation the fan clutch was shot when you fire it up and hear how loud the fan roar is supposed to be.
 
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