Benefits of a Flex Fan vs Thermo Clutch

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Looks like the thermo fan clutch is losing it on my '92 S-10, the fan spins pretty easily by hand. Engine temps (and AC) are rising, especially when idling in the summer heat. (Cooling system was flushed a few years ago, and engine temp quickly drops at highway speeds, so the thermostat is probably OK, and no leaks seen on water pump, coolant level not dropping, etc) I was in Autozone looking for a replacement clutch, they will need to order one. The guy at the counter said I would be better with a flex fan (which also needs a spacer added), but that is like double the price of replacing the clutch. He said the flex fan will give much better air flow then the stock fan with a clutch. Any opinions out there?
 
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Wow, those are some old posts on that forum link, lol. It started back in 2001! But alot of useful input by people who have tried different types of cooling fans.
 

KilgoreBass

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Thanks Steve, I think I will stick with the thermo clutch. I also did some Googling, and see that a Flex Fan might make engine warm-up an issue in the winter, since its always engaged.
 
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Don't have much experience with either in real life other than doing replacements. But understanding how both work I would stick with the OEM design. Especially because you might be driving that engine a long time because they are pretty much bullet proof. Sorry about the age of those posts, best real world info I could find.
 
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Flex fans are garbage. For starters you have a clutch on your stock fan to improve gas milage and decrease noise. Put on a flex fan and your MPG will take a major hit. Flex fans flatten out at higher rpm's. Eventully they flatten out and stay.......No longer move air as designed. This probly does not apply to you but never put a flex fan on a heavy vehicle or one used for towing. Say your in a motorhome and you have a flex fan on it. You come to a steep hill, you downshift to pull the hill. The engine revs up to say 3500 rpm, The flex fan flattens out..........No longer pulling air but blocking it from going through the radiator. Engine overheats, blows head gaskets, cracks the heads etc. I see this every year when somebody puts a flex fan on a motorhome then tries to pull a toyhauler full of atv's up cajon pass. I bet that the clown that recomended a flex fan does not know that you have a reverse rotation waterpump and you would need a reverse rotation flex fan which are pretty rare. Stick with a fan clutch.
 
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I had an 88 S10 with 4.3, it required a reverse rotation flex fan, check yours before you buy. After I got the right bolts, the spacer and the right fan, it worked great.
 
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Always been a fan of electric fans myself. Much nicer to drive, as you don't feel the constant fan drag in hot weather.
 

OVERKILL

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They are garbage. They move the most air when you don't need it: Low RPM They move the LEAST air when you DO need it: Higher RPM A clutch fan on the other hand: It moves the most air when it is needed to: When it gets hot enough to lock-in. It is otherwise essentially idling on the shaft, providing far less drag than when it is fully engaged, but WILL engage when necessary. Sounds like a no-brainer to me.
 
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Actually, I would imagine the airflow delivery of a flex fan would be somewhat constant. While at low RPM their rotation is slow, but the blade pitch is the greatest. As RPMs increase, the blades flaten out...but the rotation increase should offset this. That said, the constant fan drag would be annoying. Helicopters sometimes reduce rotar pitch, but increase rotation speed for "stealth" operations, as it reduces the chopping sound. They create the same lift, but use more fuel due to reduced efficiency.
 

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 Originally Posted By: pzev
Actually, I would imagine the airflow delivery of a flex fan would be somewhat constant. While at low RPM their rotation is slow, but the blade pitch is the greatest. As RPMs increase, the blades flaten out...but the rotation increase should offset this. That said, the constant fan drag would be annoying. Helicopters sometimes reduce rotar pitch, but increase rotation speed for "stealth" operations, as it reduces the chopping sound. They create the same lift, but use more fuel due to reduced efficiency.
They go completely flat (flex fan blades). And, as another poster mentioned, they eventually remain bent and move a lot less air even at low RPM's. A good friend of mine has one that his dad had run on his S-truck, and it has the "perma-bent" blades. They bend right where they mount to the rigid centre structure, so that they are shaped like a "C".
 

KilgoreBass

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Thanks for the all the input, no Flex Fan for me! Funny how they are really pushing these lately, I also say Flex Fans prominently displayed at an O'Reilly a few weeks ago, hanging up behind the counter... PS: actually, the guy at Autozone did know it was a reverse rotation fan after looked up my vehicle, and saw it had a serpentine belt. Not sure if he saw that on the computer, or just knew it, but at least there are some people working at the parts stores with a bit of experience....
 

KilgoreBass

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I wonder what kind of stress failures might develop over time on a fan that is always being "flexed" into different pitch?? Last thing I want is a fan flying apart.....
 
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Flex fans do come thru hoods when they get stressed I see a couple of flex fans tragedies. Lucky i was not around any of them. Clutch fan all the way
 

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 Originally Posted By: RH+G
Flex fans do come thru hoods when they get stressed I see a couple of flex fans tragedies. Lucky i was not around any of them. Clutch fan all the way
When maximizing HP, my choice is electric. I run a Taurus SHO fan on the Mustang/Capri and a Lincoln Mark VIII fan on the Town Car. Increases fuel mileage, decreases warm-up time, and frees up power. Don't know if I'd ever put one on a truck though.....
 
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Aren't there trucks coming with electric fans now? Some electric fans can really move some air, and you can always use more than one...assuming they would fit.
 
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 Originally Posted By: pzev
Aren't there trucks coming with electric fans now? Some electric fans can really move some air, and you can always use more than one...assuming they would fit.
My Sierra came with two electric fans, side by side. The rad is wide but short, so two fans are needed to cover the rad properly. I had a 1982 Mazda B2000 pu that came with a basic fan, not flex or clutch. I took the fan off and installed a electric fan and the fan would turn on maybe 1% of the time. I saved a bit of fuel by using the electric fan.
 
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The partially correct theory of a flex fan is that they push a lot of air at low speeds, but not at high speeds, when the vehicle's speed causes a lot of air flow through the radiator. This omits the concept of gears and high RPMs at lower speeds, however.
 

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 Originally Posted By: pzev
Aren't there trucks coming with electric fans now? Some electric fans can really move some air, and you can always use more than one...assuming they would fit.
The Mark VIII fan is probably the most insane air mover of them all. I would just assume the reason most OEM's didn't used them was for some sort of reliability thing..... Of course I've never had an issue with either of mine....
 
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