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Fan Clutch check

T

tnjeff

NAXJA Forum User
Location
Tennessee
I searched but I can't find. I forget, how do you tell if a fan clutch is bad. My 96 xj is running hot (228-235). When I got home I spun the fan by hand and it spun pretty easily. I can't remember if it was supposed to spin easily when hot or cold.

Had a new water pump about 2 years ago and radiator flushed last year. My temp gauge doesn't work. I just noticed that my efan was coming on pretty regularly so I hooked up my laptop to the OBDII port and read the temps from there.

Thanks
 
The clutch engages the fan as the engine temp rises. So at that temp the fan should be fully locked.


There is a method of testing them with a voltmeter that I'm not familiar with.
 
LYKOS said:
There is a method of testing them with a voltmeter that I'm not familiar with.
Click to expand...

it's a thermostatic clutch, no electrical. you cannot check it with a voltmeter.

give it a spin, even when cold it shouldn't continue spinning more than the width of one fan blade once you let go.
 
GrimmJeeper said:
it's a thermostatic clutch, no electrical. you cannot check it with a voltmeter.

give it a spin, even when cold it shouldn't continue spinning more than the width of one fan blade once you let go.
Click to expand...

Thats what I thought but I saw somewhere on here someone testing one with a voltmeter.

B ut from the looks of it its a simple viscous clutch.
 
Thanks guys, that's what I thought. I went and bought one. I'll let you know. Could be more than one thing but I think the fan clutch definitely needs replacing.
 
Well, it doesn't look like it's any better. I replaced the clutch and drove around the neighborhood for a few minutes and it read between 223 - 226, with a high of 232. Air temp outside is about 85. The electric fan came on pretty quickly.

I was hoping for a temp in about the 210 range. What would be considered a good operating temp given the conditions (neighborhood driving, stop signs etc.) and how hot is too hot?

Thanks
 
210 is normal operating temp. feel the radiator with your hand after you shut the jeep off (don't need you losing any fingers :gee:). it should be the same temp in all areas, if there is a cooler spot on it you have a plugged up radiator. feel the top hose, is it hot? if not you have a thermostat that is stuck shut. just a couple things to check that won't cost you any money.
 
Thanks Grimm I'll check those. If 210 is normal, and I realize that's what I'm shooting for, what would you call too hot? That might be a bad question as in, what's not too hot for one jeep might be way too hot for another?

Edit-
Just checked. Couldn't tell much about the radiator because it's under that metal piece. Cap was hot though. The top hose was also hot.
 
Last edited:
you should be able to fit a finger or two at least through the blades of either fan to see if both sides of it are hot.

I would say your temps of 230+ are WAY too hot.
 
I can do that. Do you know of any good way to check the water pump? It's not leaking or making any noise. I'm wondering if the impeller blades are rotted off of it. Anyway, thanks for the help. I guess now I'm into the "general overheating problems" territory.
 
waterpumps are cheap and easy enough to swap out, if you don't know the last time it was changed (if ever) I would start there and put a new thermostat in it. 9 times out of 10 though it's usually a plugged up radiator.
 
Fixed. Put in a Stant 195 degree t-stat and new hoses. Took it for a drive and the hottest it got was 207. The fan clutch didn't hurt though. I don't know how old the one that was on there was.
Thanks again for all the help.
 
The fan clutch will affect your temps on the trail a lot more than on the road unless you're in stop and go traffic - when mine failed I didn't realize until a full throttle assault on a ledge resulted in a bad overheat.

Smart move replacing the thermostat before the water pump, it sure is easier to get to and a lot cheaper.
 
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