Fixed Flex Fan - Complete DIY Part Number List

kapalczynski · **Posted:** Mon Apr 05, 2010 7:56 pm

ITS GOT A NAME!!! - I call it the FFF Mod - Fixed Flex Fan.

Some of you may have followed this a little on the thermostat ideas topic. I have now got the setup created, so I started a new topic for this:

Heres the basic background.

The fan clutch design on the CRD's seems to wear out rather quickly. In fact, the fan clutch on many of the CRD's has gone out, and most of us didn't have any clue until we went up a hill or towed for the first time in awhile and started running a little hot. Then you either baby it home or are stuck in the middle of nowhere and a replacement part has to be ordered.

Here's my solution:

I just put on the new flex fan and adapter setup I came up with. had to make a spacer (machined 2 1" washers out to 31 mm to allow clearance of fan blades - were too close to accessories). It looks sweet and DEFINITELY moves a lot more air than the factory fan/clutch even when it was locked up.

Definitely louder than a stock fan/clutch that is not locked, but sounds pretty mean and powerful. About the same noise as a fan and clutch thats locked up, a little bit of a smooth whine at high rpms, loudest at 3k rpms, starts to flex at 3K RPM's, probably half flexed at 4K rpms. Quites down a bit from 3k as it reaches towards 4k rpm peak.

I probably should have taken some photos out of the car, but here it is installed. It weighs almost exactly half the weight of the factory setup and is MUCH less rotational mass since it is not as heavy at the outer area of rotation either. All the mass in the flex fan/adapter is very close to the center of the rotational area so it will be interesting to compare economy on this next tank. I am hoping the greatly reduced rotational mass economy gain will outweigh the small loss in economy that will occur due to the fan having a direct connection and not on a clutch setup.

If you tow or are worried about staying cool, this will definitely move much more air and be more reliable than the fan/clutch setup and IT WILL NEVER GO OUT. Most fan clutches on all our jeeps already have (mine was out since I purchased the vehicle at 78K miles). I didn't even know mine was toast untill I pulled it out and found that after a couple turns with my hand it moved freely. This seems to be the case with most of us...we find out when we tow or pull a hill that it was already bad.

After an oven test of 220* and an hour later it still failed and did not grip any different than when cold. It would rotate completely free after a few turns, and could be spun and spin several rotations freely. Thankfully our jeeps cooling system is fairly robust and in the past I only had one issue getting a little hot, even with a bad fan clutch. That is why I wasn't sure it was bad until it was removed and tested.

Anyway, a new fan clutch (just the clutch) is $142.00 from Jeep plus shipping and may go out again in several thousand miles. The problem is you may not know it is bad until you are going up a hill or towing and start overheating as was my case.

This setup comes in at the $100.00 mark including, the Flex fan, the spacer, the adapter, and all hardware and will not go out again.

Here is a profile view:

Part numbers and prices to complete the kit:

Flex Fan - Imperial Part number 223619 - 19" reverse direction High flow flex fan(Advanced auto - free shipping from local store - $28.99):

Adapter - Flex-a-lite part number 851 - 30 mm x 1.5 pitch flex fan adapter (Amazon.com - $43.07 - free shipping):

Washers (used as spacer to allow clearance between engine accessories) - McMaster-Carr part number 93849A112 - (2 needed) (mcmastercarr.com - $4.58 each-2 needed plus shipping cost):

NOTE!!! These washers you won't be able to get from your local hardware store, not a normal size. Our ace hardware, lowes, home depot did NOT have them.

*EDIT* Just a note: any 31mm washers will work, thickness should be around 3.5-4.5mm thick per washer and need about 2 depending on thickness. The following part numbers will work, but are either not stainless steel or are larger outside diameter (will stick out more but still function fine) than the earlier mentioned part number: 91166A340, 91455A220, 98035A112, 93475A350.

You will also need 4 bolts and 4 lock washers to fit the spacer found at local hardware store.
Total cost about $100. Cheaper than a fan clutch alone.

LibertyCRD · **Posted:** Mon Apr 05, 2010 8:46 pm

Removing the clutch fan altogether is one of the best things I've done yet.

Right now I'm in the Appalachian Mountains running around in 85 degree ambient temps between stop lights and my temp guage will not even go past the half-way mark.

kapalczynski · **Posted:** Mon Apr 05, 2010 8:58 pm

LibertyCRD wrote:

Removing the clutch fan altogether is one of the best things I've done yet.

Right now I'm in the Appalachian Mountains running around in 85 degree ambient temps between stop lights and my temp gauge will not even go past the half-way mark.

So...you are running NO fan?

That is basically where I was with a toast fan clutch I guess...most of the time its fine...sometimes its not...

I was running warm (3/4 on the gauge) up a long twisty road uphill at speeds between 35 and 45 mph w/torque converter locked (3rd gear)...just not enough fan with bad fan clutch and not fast enough speed to get much air through the radiator.

racertracer · **Posted:** Mon Apr 05, 2010 9:26 pm

LibertyCRD wrote:

Removing the clutch fan altogether is one of the best things I've done yet.

Right now I'm in the Appalachian Mountains running around in 85 degree ambient temps between stop lights and my temp guage will not even go past the half-way mark.

Question is, does it run hot in the heat of the summer? How does your vehicle fare in 110 degree temps, without the use of a radiator fan?

RTStabler51 · **Posted:** Mon Apr 05, 2010 9:51 pm

so by this new setup your fan is always pulling air?

JL Rockies · **Posted:** Mon Apr 05, 2010 11:03 pm

Isn't the purpose of the clutch to reduce parasitic drag? Wouldn't a system like this make it difficult to get to operating temps in cold weather?

MrMopar64 · **Posted:** Tue Apr 06, 2010 2:32 am

Which flex fan are you using in the kit? A Flex-a-lite, the generic autozone special, etc?

LibertyCRD · **Posted:** Tue Apr 06, 2010 9:40 am

racertracer wrote:

LibertyCRD wrote:

Removing the clutch fan altogether is one of the best things I've done yet.

Right now I'm in the Appalachian Mountains running around in 85 degree ambient temps between stop lights and my temp guage will not even go past the half-way mark.

Question is, does it run hot in the heat of the summer? How does your vehicle fare in 110 degree temps, without the use of a radiator fan?

We rarely get to 110 here. A couple of Summers ago, we hit 105 on a few days. But most of the time 95 is about the hottest it'll get.

My thinking is....if this Jeep can handle 85 degrees running around in the mountains in stop and go traffic without even hitting the half-way mark on the temp. guage.....then it should be just fine in 95 degree weather also. Remember...according to GDE it's perfectly fine to have the needle slightly above half-way.

And with NO clutch fan...you've removed weight and drag, improved fuel economy, and according to some....the added running temperature further increases fuel economy.

racertracer · **Posted:** Tue Apr 06, 2010 11:15 am

LibertyCRD wrote:

My thinking is....if this Jeep can handle 85 degrees running around in the mountains in stop and go traffic without even hitting the half-way mark on the temp. guage.....then it should be just fine in 95 degree weather also. Remember...according to GDE it's perfectly fine to have the needle slightly above half-way.

And with NO clutch fan...you've removed weight and drag, improved fuel economy, and according to some....the added running temperature further increases fuel economy.

How long have you been running the jeep without a fan & fanclutch?

JL Rockies · **Posted:** Tue Apr 06, 2010 3:15 pm

That wouldn't fly out here, very hot summers and lots of (real) mountains.

kapalczynski · **Posted:** Tue Apr 06, 2010 6:29 pm

RTStabler51 wrote:

so by this new setup your fan is always pulling air?

Yes, the Flex fan would be a directly connected setup. Always pulling air. Less rotational inertia , but always connected. At hwy cruise there is already so much air flowing through the radiator the hwy economy probably won't be hurt at all. City mileage may or may not change. Less rotational mass, but always connected...may or may not hurt city economy, currently testing this now.

kapalczynski · **Posted:** Tue Apr 06, 2010 6:38 pm

JL Rockies wrote:

Isn't the purpose of the clutch to reduce parasitic drag? Wouldn't a system like this make it difficult to get to operating temps in cold weather?

"reduce parasitic drag" - Yes, the idea of the fan clutch is the engine can rev up and down w/o the fan having to keep up there by allowing for better economy. This new setup weighs HALF the stock setup and shouldn't hurt economy too much. The loss from being connected may be gained back by the less mass needing to be spun up. I am willing to bet the less mass and closer to the center of the fan will take 1/3 the effort to spin up as a connected fan clutch and fan. This is what I am testing.

"difficult to get to operating temps in cold weather" - No, this has nothing to do with getting to operating temp other than the fact that moving more air may cause a tiny bit of drag on the engine. It may even cause it to warm up a little bit faster with some drag present. Air moving through the radiator makes no difference on the engine temp UNTIL the thermostat is open and coolant is circulating through the radiator. Coolant in the radiator is NOT moving UNTIL the thermostat opens after the engine hits the operating temp. This will only ENSURE the engine will not exceed the operating temp even loaded down and towing up a hill.

- This should also make the intercooler more efficient as more air will be moving through the intercooler as well, and less power loss from heated compressed air will occur. This may be negligible at low boost, but may help a lot at high boost where the fan is moving a lot of air. Hot compressed air is never good for the engine.

kapalczynski · **Posted:** Tue Apr 06, 2010 6:58 pm

MrMopar64 wrote:

Which flex fan are you using in the kit? A Flex-a-lite, the generic autozone special, etc?

There are not alot of choices for brands of flex fans out there, but I chose Imperial brand flex fan due to personal experience with their reliability (not that much could go wrong with a piece of metal...lol) and a co-workers experience.

I ran one on a balanced and blueprinted 383 stroker that occasionally hit 7000 rpm's, and routinely hit 6500 rpm's. Unfortunately the rear main seal couldn't take those rpm's, even though the engine could. lol I found that above 6000 rpm's they like to go out frequently.

I was just talking about the flex fan idea at work with My co-worker the other day. He's a ground station engineer (really freaking smart guy) and is into cars, and even though he's pretty well off, he keeps his cars forever and maintains them till they rust through. He's had this brand on his fullsize V8 cargo van to improve air flow for towing (that is the sole purpose of his van) and has had it on his vehicle ~200,000 out of the ~ 258,000 miles he's had the van(from the lot new in 1980's lol). Yes, believe it or not, ~200k miles. Like I said, he is the type of guy that keeps all of his vehicles until they rust through the frame. lol He just traded in his old ford minivan (~270,000 miles on it) with the cash for clunkers program for a hybrid toyota hylander. Then he proceeded to show me that the economy of the hybrid would make up for the full replacement of the batteries in 10 years over a regular non hybrid hylander.

So far the flex fan on the jeep has performed awesome, I took a 5.6L titan on the highway when he started screwing around with me...

lol I've hit the 4k mark of our engine several times and it sounds GREAT. Sounds a little like a supercharger at those rpm's.

kapalczynski · **Posted:** Tue Apr 06, 2010 7:07 pm

LibertyCRD wrote:

racertracer wrote:

LibertyCRD wrote:

Removing the clutch fan altogether is one of the best things I've done yet.

Right now I'm in the Appalachian Mountains running around in 85 degree ambient temps between stop lights and my temp guage will not even go past the half-way mark.

Question is, does it run hot in the heat of the summer? How does your vehicle fare in 110 degree temps, without the use of a radiator fan?

We rarely get to 110 here. A couple of Summers ago, we hit 105 on a few days. But most of the time 95 is about the hottest it'll get.

My thinking is....if this Jeep can handle 85 degrees running around in the mountains in stop and go traffic without even hitting the half-way mark on the temp. guage.....then it should be just fine in 95 degree weather also. Remember...according to GDE it's perfectly fine to have the needle slightly above half-way.

And with NO clutch fan...you've removed weight and drag, improved fuel economy, and according to some....the added running temperature further increases fuel economy.

Increasing the temp to a certain point increases economy...I'm not exactly sure what temp our engine is most efficient at, but if you run a little warm, then find a hill, etc, you're in trouble. I would at least carry the fan with me in the car just in case.

I would rather run a higher temp stat and a good fan and KNOW I will never overheat than hope for the best.

My economy comparisons will be with my bad fan clutch/fan and the new flex fan. It was already like it wasn't there since it was free spinning so we'll see how much economy you really save. I doubt it is more than a mile to the gallon, and even so it would not be worth running the risk of overheating if the circumstances happened to let it. Our engine, with the aluminum head and iron block, is already a disaster design to overheat due to the different expansion rates of aluminum and iron. I can pretty much guarantee a blown head gasket in overheating conditions.

The risk of several thousand dollars worth of damage is not worth saving a mile to the gallon or two for me.

racertracer · **Posted:** Tue Apr 06, 2010 7:35 pm

I already bought the fan clutch, just haven't installed it yet, but If I knew you were going to come up with another cool modification I would have waited.

europachris · **Posted:** Tue Apr 06, 2010 9:28 pm

What makes the CRD fan clutch more prone to fail than any other application? Crappy Chrysler part to begin with? :BINGO:

Viscous fan clutches have been around a long time, but frankly, I don't see how they ever actually work properly or reliably - that's just the engineer in me talking.

What we REALLY need is an electric fan clutch like the Class 8 highway tractors use, and you could even put in a manual override switch to cut out the fan for a momentary "boost" for passing, etc. Otherwise, the fan would be thermostatically controlled just like a front wheel drive car except the engine would provide the fan power rather than an electric motor. You could even combine the fan clutch with a flex fan for the best of both worlds.

Chris

LibertyCRD · **Posted:** Tue Apr 06, 2010 9:36 pm

I realize that the Rockies are a greater mountain range....but I hardly consider 6,000+ ft. elevation to not be a "real" mountain. Today...we hit 91 degrees here. I ran the A/C on it's highest possible setting for a while, and also drove up into the mountains to see black bears with the family with the A/C off (no e-fan running) for a while too. In both cases, the temp NEVER crossed the half-way mark on the guage.

It is becoming more apparent to me that the clutch-driven fan is nothing more than a paper weight on these particular Jeeps. Why spend the money to fix it? Just take it off.

Goglio704 · **Posted:** Tue Apr 06, 2010 10:09 pm

I've heard my belt driven fan clutch in on two occasions. The first time was driving slow in loose sand. The temp gauge climbed to about 3/4 of scale. The fan clutched in, and the temp came down quick. The second time was crossing the continental divide out west at interstate speeds. Same as before - gauge climbed, fan screamed, and the temp came down. So, I've only needed it twice in more than 60k miles, but when I needed it, it was there.

JL Rockies · **Posted:** Tue Apr 06, 2010 11:20 pm

6000 ft is the bunny trail yo.

onthehunt · **Posted:** Tue Apr 06, 2010 11:34 pm

[quote][What we REALLY need is an electric fan clutch like the Class 8 highway tractors use/quote]

They are air controlled. Not really an option. They work the same way as a viscous clutch. The only benefit is longer lasting and rebuildable. I can't see gaining anything with a flex fan. Nice work though. Not trying to rain on your parade.

Fixed Flex Fan - Complete DIY Part Number List

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