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flex fan vs fan clutch

4055 Views 42 Replies 8 Participants Last post by  xjy173
i have a friend with a 97 tj that the fan clutch is going bad. he said a new one was $120. ouch. is there any reason not to replace it with a flex fan?

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Before I'd pay that for a flex fan I think I'd check out a good electric
fan setup. It should cool better at slow speeds and give you a few more
ponies. Just my opion.
Electric is the way to go.

If I remember correctly:
I helped my friend replacing his damaged fan clutch. If you asked from a dealer, that's the price you're getting (around $ 100).
I got his from Track Auto, about $ 20. I think it's compatible with the earlier YJ clutch.
So you may want to consider that instead.
We replaced it about a year and half ago and it's still working fine.


Flex fans are LOUD, sound like an airplane. Go electric or or stock.

Brad (from the 4 Wheeling center of the universe, 4 corners USA)
I got electric and I love it, cools awesome when on slow trail rides.

Is the reason you up the HP with an electric fan because you don't have the additional drag on the engine?

Who's a good manufacturer for the electric fan? Should you go larger than stock? After my last run up the Sierra's, I'm looking for cheap HP's! /wwwthreads_images/icons/cool.gif

I6, 3.5" Black Diamond, MORE, & more
[email protected]
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Hey YJ94, the electric fan does up the HP because of less drag on the engine but honestly I couldn't tell the difference. But besides that they are great for deep water crossing because you can manually install a switch. Flex-a-Lite makes good fans, check them out at and if you want to see one installed I did a write up on mine....

YJ94- Where did you go recently that you needed more power? I just did John Bull on Saturday and had a great time.... of course a 4 cylinder going up to Big Bear is a 3rd gear and 3000 RPM experience.

95.5 YJ with "stuff"
I know, I know, completely off the subject, but...

John, I went skiing at Mammoth..., and found some small/short/easy dirt trails to get muddy in...

I hadn't driven long distances with my lift (yet), and larger tires (31's)...

Well, maybe I'm spoiled, but I don't see going up the mountian in 3rd as a positive... I used to fly-by everyone in 5th! Now I barely make the pass in 3rd... I need to regear, especially once I put on 33's/12.50 and a 1" body lift!

Where is John Bull in Big Bear? I usually just drive to Gorman (about 30 miles from my house) and mess 'round on the trails/safety area. There are only a few technical spots there.. Maybe we should start a new thread: Off-roading in SoCAL....

I6, 3.5" Black Diamond, MORE, & more
[email protected]
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Answering the original question.............a flex fan is ill advised on these "high rpm/low ground speed" applications. No airflow and air flow ......bad combo. Go electric


/wwwthreads_images/icons/smile.gif There is people on this board that know the truth of this but here
is what I have been told by some people that i thought knew what they where
talking about on the FSJ mailing list ./wwwthreads_images/icons/smile.gif

1. Go with the high price fan clutch the cheap ones don't last.
If you have the room for the clutch and fan on the end of your
water pump {which you do} the clutch fan is the best way to go
as your auto engineers all ready knows.Best at every thing but
water crossings. {elec. you can turn off.}

2. When you are going down the road and the engine can cool itself with
the high air flow the fan will not be draging down your engine horse
power because it will be free wheeling because of the clutch.

3. Flex fan has alot of some what bad points-does nothing great every
thing it does is half A##. Still drags at hiway speeds ,does not move air
the best a low speeds , will suck easyer into your rad. in water.
CHEAP FIX IS ALL./wwwthreads_images/icons/shocked.gif

4. Eletric fan at low speed will move air that is true but if it takes 2 horse
power to turn your engine fan it will take two horse if it is on the end of
your water pump or a wire off of your alt.. /wwwthreads_images/icons/tongue.gif/wwwthreads_images/icons/frown.gifTHERE IS NO FREE
RIDE/wwwthreads_images/icons/frown.gif/wwwthreads_images/icons/shocked.gif If there was we could build a perpetual{SP} motion
You can turn off a eletric fan for water crossings.
One guy on the FSJ list ran a eletric fan infront of his rad. in the
S.W. so to run more air over his air cond. at the stop lights so
so he could stay cooler. Thought that was a nice idea./wwwthreads_images/icons/smile.gif

Where is dorfs,CJDave,GeeAea/wwwthreads_images/icons/laugh.gif
/wwwthreads_images/icons/shocked.gif Help me or shot me /wwwthreads_images/icons/shocked.gif
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You're right on the money!
flex fans suck although they have made me a fair amount
of money replaceing them so I shan't complane.

85'CJ7 258 4" runnin33's
Hey gregg, you say in #4 that an electric will run off water pump or alternator and suck 2hp, but I have mine wired directly to my battery through a relay, that takes up no HP, correct??

The more load on the alternator; the more power it needs from the engine to turn at a given RPM. So somewhere that fan load is being carried by the power plant.

I would guess that clutch fans are more efficient than an electric, simply because on most front drive cars, there are two electric fans hung on the radiator. If those engines were north/south, then they would have one clutch fan to do the same work.

XJY173 Is correct in my way of thinking.
I do not know how much HP a fan uses. Just grabed 2HP out of the air.
My point as James points out is X=Hp of fan to cool said motor.
It will use same X=Hp if off the end of the water pump
{like clutch fan or flex fan}
Or off the alt. or batt.
{like a eletric fan}
Get down to ground level it might take a pinch more Hp to run a
eletric fan with the loses of running the fan belt-turning the alt.and
running the power down that little wire to the alt. or batt.
/wwwthreads_images/icons/smile.gif only CJDave would come up with a way to measure the loses /wwwthreads_images/icons/smile.gif

/wwwthreads_images/icons/wink.gif Was it LarryM that said some of
his moon guys had part time at Wal-Mart./wwwthreads_images/icons/wink.gif
I think I saw some of them last week they look cute with there little
cowboy hats/wwwthreads_images/icons/wink.gif/wwwthreads_images/icons/tongue.gif/wwwthreads_images/icons/smile.gif/wwwthreads_images/icons/shocked.gif/wwwthreads_images/icons/mad.gif/wwwthreads_images/icons/laugh.gif/wwwthreads_images/icons/frown.gif/wwwthreads_images/icons/crazy.gif/wwwthreads_images/icons/cool.gif
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for your reading pleasure...

85 CJ7, 350TBI ,T19 4spd
'00 TJ Sport, NV3550 5spd, D44, Teraflex system
I think one of the things you are not considering about the HP used by the fan is that the electric runs
at a near constant speed whereas the speed of the mechanical is a direct function of engine speed.
Assuming that the mechanical fan will cool the radiator at idle, there is wasted HP for any engine speed
above that. The electric fan would have a constant current draw on the electrical system whether at idle
or at red line.

Another consideration is that the air movement through the radiator at highway speeds has greater
benefit on the electric fan since it would draw less current with the air helping to turn the fan. Taking
this to the extreme, the fans would charge the battery. This benefit is not realized with the mechanical
fan and can actually hamper the air flow.

The mechanical fan also acts as a light flywheel resisting changes in engine speed meaning more HP to

All of the above are minor points. What is important is:

Electric fans cool much better. My engine temp runs slightly lower in stop and go traffic than at 70MPH
on the interstate. It will actually drop a noticeable amount while stopped at the first traffic light after I get
off of the highway.

The mechanical fan also acts a gyro and puts excessive pressure on the water pump bearings. The
electric does not.

I am running the two fans that came out of the same '88 Firebird that provided my 305 TPI engine. These
fans are quite a bit smaller than an engine mounted fan, only about 12" diameter and do a much better

I would never go back to a mechanical fan.

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Taz you have a complex post here.

At rock crawling speed a motor goes to work off idle at a little higher rpm.
the fan turns faster but the motor working harder but hopefully staying cool.
If that was the case one could say the electric fan is over kill at idle and
useing more power than need be.
At highway speed one would hope that the eletric fan would be off because
the air flow over the rad should take care of it and the thermostat should
have the fan off. but the eletric fan on the front of the rad would be blocking
more air flow thru the rad.
On a clutch fan the clutch should be disengaged and it would be free wheeling
and not working like a flywheel.
No B.S. here I wonder about your cooling system and your engine temp. changeing.
If your cooling system is doing its job the temp of your engine should not
change. Your thermostat should keep the temp even. Even at 70mph. should
be able to throw the fan away, in fact it should be out of the picture.
How low are your gears?????
WE got things here like thermostats ,clutchs, how good of shape rad is in,and gears.
Alot of variables here thats why I called it a complex post.
Makes for a good discussion .
All of this is just MHO.

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I have a friend with an 1988 Chevy S-10 Blazer that had a clutch fan lock up on him, meaning the fan wouldn't freewheel at high airflows across the radiator. He experienced exactly what Taz described, which is essentially a straight mechanical fan. He could not go over 45 MPH because of all the vibration and noise. Both electric and clutches eliminate this problem.

Perhaps Gee Aea has the correct idea by just answering the original post. However, I am always grateful for the people on this BBS for their time, courtesy and their knowledge. I once told CJ Dave and I repeat myself here: I'm glad I bought my Cherokee and became a member of the Jeep Owners Club. You guys are great! It is a pleasure debating and learning from you all. /wwwthreads_images/icons/smile.gif

Best Regards,
Jim young
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