Radiator Fan clutch - JeepForum.com
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post #1 of 44 Old 01-17-2016, 08:03 AM Thread Starter
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Cj Radiator Fan clutch

I have a 1985 CJ 258 6 cylinder 5 speed transmission. No AC , no power brakes but I do have power steering. While driving in stop and go traffic after only a mile my radiator boiled over and I shut the engine down. After cooling down I was able to add some more water and start up again. I don't know the cause of this and wanted to know where to look before I start replacing parts. I am assuming since the radiator water was hot and boiling that the thermostat worked to get flow from the engine. So I am guessing it has to do with the fan or the fan clutch. The fan has 7 blades and it is original . When the engine is shut off I can spin the fan freely. When the engine runs the fan spins and as I increase the RPM on the engine the fan spins faster BUT I can actually grab the fan when the engine is running and stop it from spinning. Yes I can. Now that doesn't seem normal , or maybe I am not normal that I can actually grab it while it spins. I still have all my fingers. Is this the problem I have with overheating? I live in South Florida and the temps weren't too hot that day but in the 80's anyway. If it is the fan or the clutch , do I replace just the clutch or replace the fan and install one with out the clutch ? Any thoughts? I am not sure if this is the problem or not but that is what I am guessing. Also , why not just remove the thermostat all together and let the water run freely though the engine?
Thanks for the insight.....

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post #2 of 44 Old 01-17-2016, 08:16 AM
1949er
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You want a Thermostat ! best is a OEM at 195 deg. , I could not find at the time a fan clutch for my CJ7 a went with a flex fan with no shroud it doesn't overheat .
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post #3 of 44 Old 01-17-2016, 08:19 AM
Dryseals
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With the engine not running, you should be able to spin the fan but there should be a fair amount of resistance, no free spinning, your fan clutch is bad.

As for removing the thermostat completely, your engine may never get up to operating temperature, which equates to reduced performance and also causes a build up of acids and moisture in your motor oil which over time can damage your engine.
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post #4 of 44 Old 01-17-2016, 08:34 AM
Mike Romain
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When your engine is hot and shut down, there should be some pretty heavy drag on the clutch. When you shut down a hot engine, the fan should stop almost immediately, if it freewheels, it is done.
Be sure you get the proper replacement. V-belt system uses normal rotation, serpentine belt system uses reverse rotation.

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post #5 of 44 Old 01-17-2016, 08:59 AM
Shawn Watson
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Bad clutches usually mist oil out of the front (at least the thermos do) so that's a tell-tale sign of a gonner.


Shawn

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post #6 of 44 Old 01-17-2016, 09:11 AM Thread Starter
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Fan

So it appears that with the tests of the fan free wheeling it is most likely the fan clutch.There isn't any oil leaking from it though. I have V belts on the pulleys. So I can order a new clutch but also wanted to know if there is a specific brand or place to buy them from. I see on Ebay that they sell for between 45 to 70 bucks but I don't really know what I am getting as far as quality. Any recommendations here? I don't recognize the name on the parts that are listed on the site so I am not sure which to choose. Ive had parts from Auto Zone that were bad within a week.
So it is best to keep the T-stat in . How do you know what temp stat to use for my area? I do mostly lower speed driving in hot humid weather 0-45MPH. Is the temperature opening point stamped on the t-stat?
What is a flex fan? Does that eliminate the clutch all together?
I just want to do it right the first time.
Thanks
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post #7 of 44 Old 01-17-2016, 09:27 AM
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The problem I had finding a viscous clutch was all replacements I found had fins that decreased the clearance to the Rad that's why it got the flex also being pushed for time on a Jeep trip and had the flex on hand , you might check into the Hayden brand , as stated before run factory thermostat temp of 195deg. where your motor want's to run correctly and they start to open in the range of 180-185 & full at 195 .
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post #8 of 44 Old 01-17-2016, 09:29 AM
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Your engine is designed to run on a 195* t-stat. That's what you need.

When cold, your fan clutch should have only slight resistance. It shouldn't free wheel, but you should be able to spin it about 1/2-turn by hand. When the engine is hot, there should be much more resistance.

I've had good luck with the Hayden brand fan clutch.

http://www.summitracing.com/parts/hd...j7?prefilter=1

Matt


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post #9 of 44 Old 01-17-2016, 09:44 AM
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The Hayden clutch should do the trick, just make sure it's light-duty or it'll make a ton of noise.

You can run a 180* thermostat if you want, no problem at all with dropping the temp a little (especially with the intake/exhaust configuration of an I6), but if you're doing a lot of short trips, a 195* may allow your oil to get hot enough to not build up moisture in your humid climate.

Whichever temp you choose, I'd recommend the Moroso High-Flow thermostat.




Shawn

Edit: Looks like maybe they're Mr. Gasket now

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post #10 of 44 Old 01-17-2016, 10:01 AM
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Thermostats open and close at their rated temperature. A 180 degree thermostat will make an engine run cooler than a 195 degree thermostat, but only the lower end. It does not keep the engine from overheating. AMC designed the 258 engine to operate at 195 degrees. Any other temperature thermostat or no thermostat will affect your engine performance.

My preference is a thermostatically controlled electric fan mounted on the grill side of the radiator. It has kept my 258 cool on the hottest days.
I tried the flex fan, but couldn't find a spacer I could use to clear everything. Got tired of skinning my knuckles trying to get to fit. E fan supposedly give you more HP. I haven't noticed it, but it is nice to think so.

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post #11 of 44 Old 01-17-2016, 11:29 AM
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If you have the 7 blade OEM fan, you should also have a stock plastic shroud. This is vital for proper operation.
As said. YES, use the stock thermostat.
After you replace the fan clutch, PLEASE do not test the new one with trying to stop it by hand again.....You may not be typing the same on your next post! I can't imagine trying that, did you stop it in the center? thus my fan shroud question....

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post #12 of 44 Old 01-17-2016, 12:25 PM
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You guys are cracking me up a little with the whole "designed to run at 195*" thing. That's like saying "designed to run a log manifold so you don't want a header", or "designed to run a Motorcraft so you don't want an MSD", etc.

If I was in a hot, muggy climate at sea level, you bet I'd have a cooler thermostat in there and I'd bypass the intake water heat, too!

But I digress... Hey, it's another boring Sunday


Shawn

Edit: OP, new cap while you're at it.

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post #13 of 44 Old 01-17-2016, 04:42 PM Thread Starter
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Fan clutch

I suppose it makes sense to run a cooler t-stat in it since I don't take it up to fast highway speeds , mostly in and around local . It is hot and humid most of the time. This time of year it isn't though. So which temperature is the best 195 or 180? Does 15 degrees make a big difference? It'd be cool if someone made an external adjustable t-stat to change for different road conditions.
I do still have the stock shroud on the radiator. It is about 1-3/4 inch wide.
The fan really has no drag at all so I will order the Hayden clutch from Summit based on your recommendations . I won't test the new one by hand though. As you face the radiator from the front the fan spins clockwise.
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post #14 of 44 Old 01-17-2016, 04:52 PM Thread Starter
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Clutch

Also I didn't stop the fan from the center . I was able to slow it down and stop it with engine running from the very outer edge of the fan blade. Of course dragging my hand in the same direction from the passenger side of the engine. I wouldn't try it if I thought it would harm me. It was spinning that slow. The shroud doesn't cover over the fan at all . It sits in front of it.
Also I forgot to mention I added a grill cover for looks only. It's a chrome panel with holes in it for a different look .
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post #15 of 44 Old 01-17-2016, 06:19 PM
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Quote:
Originally Posted by Safecracker View Post
I suppose it makes sense to run a cooler t-stat in it since I don't take it up to fast highway speeds , mostly in and around local . It is hot and humid most of the time. This time of year it isn't though. So which temperature is the best 195 or 180? Does 15 degrees make a big difference? It'd be cool if someone made an external adjustable t-stat to change for different road conditions.
I do still have the stock shroud on the radiator. It is about 1-3/4 inch wide.
The fan really has no drag at all so I will order the Hayden clutch from Summit based on your recommendations . I won't test the new one by hand though. As you face the radiator from the front the fan spins clockwise.
While Swatson says he would go lower, I am of a different thought especially since you say you are just running around town, if you were doing some highway then I might agree, but only in the summer temps.

Getting the oil temp up past the 200 degree F mark is critical, the recommendations are to run up in the 220-240s, this helps in removal of any moisture and other contaminants that could degrade the oil. Running a 180 stat may put your oil temperature below where it needs to be.

Just my two cents.....
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