FAQ: Is my fan clutch bad?

Sir Sam · **Posted:** Tue Nov 08, 2011 7:10 pm

Is my fan clutch bad?

Lets say your having some symptoms that may indicate you have a bad fan clutch, while driving up moderately short hills or long hills you rapidly start to warm up, only to have the vehicle cool off fairly quickly once you have crested the hill, or in general the vehicle just runs hot, well then you might have a bad fan clutch.

My personal experence was that on fairly long uphill grades, more than a mile or so, my temp gauge would start to climb quickly up to the 3/4 mark and then the vehicle would cool off very quickly after I leveled out or started going downhill. At first it was only apparently when towing but then a few months later when driving up hills that I had driven before under the same ambient conditions I noticed the vehicle getting exceedingly hot.

So I replaced my fan clutch, I went with a new hayden unit from rockauto. Here in this video you can see the old one, while fan clutches are suppose to spin freely at room temperatures they should not be this free. This unit in fact behaved normally for about 3-4 rotations then just completely let go and spun freely.

http://www.youtube.com/watch?v=XclNv2vRmt8

So if your experiencing any of the symptoms I described or your fan clutch behaves this way its probably time for a new one, go ahead and do the serpentine belt (if you haven't already) while its off as it will never be easier to do.

ATXKJ · **Posted:** Tue Nov 08, 2011 9:11 pm

If you have an 05 - odds are it's bad - from the factory

Test from the manual (per Kap)

Quote:

WARNING: BE SURE THAT THERE IS ADEQUATE FAN BLADE CLEARANCE BEFORE DRILLING.
1. Drill a 3.18-mm (1/8-in) diameter hole in the top center of the fan shroud.
2. Obtain a dial thermometer with an 8 inch stem (or equivalent). It should have a range of -18° to 105°C (0° to
220° F). Insert thermometer through the hole in the shroud. Be sure that there is adequate clearance from the
fan blades.
3. Connect a tachometer and an engine ignition timing light (timing light is to be used as a strobe light).
4. Block the air flow through the radiator. Secure a sheet of plastic in front of the radiator (or air conditioner condenser).
Use tape at the top to secure the plastic and be sure that the air flow is blocked.
5. Be sure that the air conditioner (if equipped) is turned off.
KJ ENGINE 7 - 61
WARNING: USE EXTREME CAUTION WHEN THE ENGINE IS OPERATING. DO NOT STAND IN A DIRECT LINE
WITH THE FAN. DO NOT PUT YOUR HANDS NEAR THE PULLEYS, BELTS OR FAN. DO NOT WEAR LOOSE
CLOTHING.
6. Start the engine and operate at 2400 rpm. Within ten minutes the air temperature (indicated on the dial thermometer)
should be up to 93° C (200° F). Fan drive engagement should have started to occur at between 91°
to 96° C (195° to 205° F). Engagement is distinguishable by a definite increase in fan flow noise (roaring). The
timing light also will indicate an increase in the speed of the fan.
7. When the air temperature reaches 93° C (200° F), remove the plastic sheet. Fan drive disengagement should
have started to occur at between 62° to 85° C (145° to 185° F). A definite decrease of fan flow noise (roaring)
should be noticed. If not, replace the defective viscous fan drive unit."

and Kap's Fixed Fan Mod thread -
to eliminate all concerns - scroll to page 1 of the thread
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?p=575149#p575149

FAQ: Is my fan clutch bad?

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