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Unread 06-06-2012, 06:17 PM   #1
ronjenx
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OEM Mechanical Fan Retrofit

Off road, and in stop-n-go traffic, the cooling fan on the JK comes on to cool the radiator when the water temperature reaches 215F. It brings the temperature down to about 195F, and turns off. The cycle continues until there is sufficient air flow from forward movement to keep the water cool without the fan.

Theres nothing so bad about that from the engines point of view.
However, until the fan comes on, things in the engine bay can get quite hot, including intake air temperature. The automatic transmission fluid temperature will also climb during the time the fan is off, even if there is an aux cooler installed. The aux cooler may prevent the transmission from overheating, but the fluid temperature can still get quite high when compared to the temps with sufficient forward movement.


I have been monitoring the temperatures of the engine, transmission (with an aux cooler), and intake air. The engine takes air from the engine bay, so Im using intake air temp to reflect the approximate engine bay temperature.

With all that in mind, I decided it was time to cool everything down a bit.
The only item I could think of that would address all of the temperatures listed above is a fan that turns all the time the engine is running.

I thought about adding a switched ground wire in the fan high speed relay circuit. That would work, while off road and in traffic, but the driver would have to remember to turn it on, and off when on the road. How long will the electric motor last with the extended run time?

The idea of a mechanical fan seemed like a good idea. There would always be air flowing through the transmission aux cooler, the A/C condenser, the radiator, and the engine bay. It seemed ideal.

After a little research on the forum and elsewhere, I came up with all the parts to convert from electric cooling to mechanical cooling, (kind of retro, I know).
The fan and shroud are specifically designed for the pre-2012 JK. There is also a MOPAR fan clutch available for the JK, but its over twice the price of the generic clutch. If there is a longevity issue, Ill try the MOPAR fan clutch.
Everything in the photo below is an easy plug-n-ply installation. It took about 1 hour from opening the hood to driving off for an ops check. Like I mentioned, its all designed for the JK. The stock electric fan comes out. The new fan and shroud go in.


For now, Im going with the mechanical fan and shroud. There is also an electric fan designed to work with the shroud, for added cooling in extremely hot locations. The mounting points for it are on the stock radiator frame. The JKs shipped to the Mideast have the electric fan, shroud, and mechanical fan.
I dont think the additional electric fan is necessary for the U.S. But, the option is there for those who want to have a lot of extra cooling capacity.


The mechanical fan and shroud have been installed for only a day, so I can post only preliminary results.

There is additional noise when the engine is first started. Once the fluid in the fan clutch moves to the proper chamber, it quiets down to nearly stock. On a cold start, it takes about a minute or two. On a hot start, it takes about 30 seconds.
The temps here have been in the 60sF.
Ill list the vehicles temps under similar conditions before and after the conversion. These are off road and in-town traffic conditions.
There is no real difference on the highway, as there is plenty of air from the forward movement.
Edit: Since I wrote the preceding sentence, I have learned the automatic transmission stays cooler on the highway, too.
My theory is, the fan creates a low pressure area behind the radiator, which allows more air to flow through the cooler, condenser, and radiator.

Before, the engine temp would cycle up and down between 195F and 215F
After, the engine temp stays at 195, a few degrees.

Before, the trans temp would climb to about 140F.
After, the trans temp stayed below 120F.

Before, the intake air temp would climb to 165F+.
After, the intake air temps stayed below 115F. (Im assuming this also indicates lower engine bay temps.)

Before, opening the hood following a moderate idling period, there seemed to be a lot of heat in the engine bay.
After, opening the hood following a moderate idling period, the heat seemed to be a lot less, and there was a nice breeze blowing over the engine from the fan.

Before, overall average gas mileage was around 18.5 mpg.
After, (well, its too soon to tell).

The parts involved:



The fan installed on the water pump:



The finished product:



Photo of the stock fan, and the fan used with the mechanical fan and shroud, if max cooling is needed:


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Unread 06-06-2012, 06:37 PM   #2
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Once again great stuff and great write-up.
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Unread 06-06-2012, 06:57 PM   #3
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Very nice... Let us know if everything is still peachy in a week or so I am very interested in keeping my engine cool

Also 1222 this is probably worth a FAQ write up add
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Unread 06-06-2012, 08:27 PM   #4
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My question is what was the cost to do the conversion?
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Unread 06-06-2012, 08:49 PM   #5
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Quote:
Originally Posted by Coolcatracing View Post
My question is what was the cost to do the conversion?
The parts prices are in the first picture.
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Unread 06-06-2012, 09:23 PM   #6
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Quote:
Originally Posted by ronjenx View Post
The parts prices are in the first picture.
That's what I get for tuning out once I saw the part numbers. Not a bad idea and reasoning but I'll play devils advocate and ask if a stock electric fan would last 6-7 years or more and lets say the added run time cuts that in half that's still well over 3 years on the electric fan which costs 1/2 what this setup costs. So given that in the 7 years most of us will ever have our Jeep it will still cost about the same and use none of the already limited power and mileage the 3.8L has.
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Unread 06-06-2012, 09:32 PM   #7
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Quote:
Originally Posted by Coolcatracing View Post
That's what I get for tuning out once I saw the part numbers. Not a bad idea and reasoning but I'll play devils advocate and ask if a stock electric fan would last 6-7 years or more and lets say the added run time cuts that in half that's still well over 3 years on the electric fan which costs 1/2 what this setup costs. So given that in the 7 years most of us will ever have our Jeep it will still cost about the same and use none of the already limited power and mileage the 3.8L has.
How much is the stock fan?
Don't forget, when the fan comes on, it puts an additional load on the alternator. I don't know how that compares to the mechanical fan's load, but energy isn't free.
Keeping track of gas consumption will show which one is the more efficient.
I'll report that after a few tankfuls.
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Unread 06-06-2012, 10:19 PM   #8
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Quote:
Originally Posted by ronjenx View Post
How much is the stock fan?
Don't forget, when the fan comes on, it puts an additional load on the alternator. I don't know how that compares to the mechanical fan's load, but energy isn't free.
Keeping track of gas consumption will show which one is the more efficient.
I'll report that after a few tankfuls.
The whole fan assembly costs $150, it's been proven that electric fans are more efficient than clutch types but that's also partially because they're not on all the time so having one on all the time would increase engine load like you said but on the highway electric fans are pretty much stalled anyways and use no power even when switched on where an engine driven fan is still sucking power.
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Unread 06-06-2012, 10:34 PM   #9
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Quote:
Originally Posted by Coolcatracing View Post
The whole fan assembly costs $150, it's been proven that electric fans are more efficient than clutch types but that's also partially because they're not on all the time so having one on all the time would increase engine load like you said but on the highway electric fans are pretty much stalled anyways and use no power even when switched on where an engine driven fan is still sucking power.
The stock fan assembly costs $150?

The parts for this conversion came to $183.

The idea behind the thermally controlled clutch is to minimize drag on the engine when the radiator is cool, and during highway running.

I agree, the electric fan is more efficient when it runs as designed.

I have kept good records of fuel consumption, so we'll see how it all works out.
The main purpose of the conversion is to see if it lowers engine, transmission, intake, and engine bay temperatures.
Initially, it looks like it is doing that very well.

Who knows, with the lower overall temperatures, it may even reduce the amount of oil vapors going through the PCV system.
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Unread 06-06-2012, 10:53 PM   #10
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I also wonder what the difference between operating the electric fan in low all the time versus high would be. Then it would be keeping the underhood temps down without as much engine draw or wear on the fan. So many variables to look at. And I was looking at the price for the JK specific fan clutch.
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Unread 06-06-2012, 11:23 PM   #11
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Quote:
Originally Posted by Coolcatracing View Post
I also wonder what the difference between operating the electric fan in low all the time versus high would be. Then it would be keeping the underhood temps down without as much engine draw or wear on the fan. So many variables to look at. And I was looking at the price for the JK specific fan clutch.
I mentioned the high speed fan relay because it's a lot easier to tap in a ground wire compared to tapping power into the low speed relay in the TIPM.

Tapping power into the system may cause problems. Tapping in a ground is harmless.
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Unread 06-07-2012, 08:16 AM   #12
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How much of a power difference did you notice with the manual fan installed? I ask this because I know it was noticeable on a SBC, so it must be huge on the v6. Also I thought some of the programmers on the market allowed you to change the temps that your fan turned on.
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Unread 06-07-2012, 08:33 AM   #13
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Just make sure to stay away from water now, mechanical clutches can burn up during water crossings and can even break the fan blades.

One of these days ill get around to hooking up a cut off to turn off my factory electric fan when crossing water.
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Unread 06-07-2012, 09:25 AM   #14
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Quote:
Originally Posted by gregaf3 View Post
How much of a power difference did you notice with the manual fan installed? I ask this because I know it was noticeable on a SBC, so it must be huge on the v6. Also I thought some of the programmers on the market allowed you to change the temps that your fan turned on.
In daily driving, I have noticed no difference in power. I punched it a few times to try it out. It gets up to highway speed as well as before. I say as well as before because I never had a problem with that on the stock tires and 4.10 gears.
Yes, the programmers can change the fan "on" temperature. I don't know how low they can go, but I suspect the fan will still be off for a large portion of the time off road, and in traffic. If it can be lowered to just above thermostat temperature, the result would be pretty nearly the same as the mechanical fan conversion.
Any input from those with programmers?



Quote:
Originally Posted by Noxian View Post
Just make sure to stay away from water now, mechanical clutches can burn up during water crossings and can even break the fan blades.

One of these days ill get around to hooking up a cut off to turn off my factory electric fan when crossing water.
Yeah, water deep enough to hurt the fan isn't that much of a risk for me.
I've read on the forums about quite a few electric fans not liking water, too.

The additional electric fan that is made to use in this application would be good insurance if it were installed and remained unplugged until needed.

So far the conversion is working so well it's even keeping the local air temperature down to the mid-50's.
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Unread 06-07-2012, 12:00 PM   #15
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The electric fan in the shroud is as much for the air conditioning as anything else. Most cars with clutch fans have an electric fan inside the shroud so the AC works better in slower traffic because the clutch fan really doesn't draw that much air when not locked.
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