Can any of you experts tell me if fan clutches are bi-directional? My neighbor tells me they aren't. The clutch on my '89, F250, 351 is frozen. Can I replace it with a clutch from an older 351 v-belt engine? The fan on the v-belt engine turns clock wise. The fan on my serpentine belt, '89, F250 is counter-clock wise.

 

If the replacement clutch bolts up ok, then it would work. Fan blade wise, and also with flex fans, they will bolt up but the blades have to match direction. Clutches are bi-directional.

 

Up to a point: Some heavy-duty fan clutches have CURVED elements to enhance driving torque, and thus, are more effective in one direction than the other.

impish

 

So straight finned clutches are bi-directional, curved fin clutches are best in one direction. I'm swapping a pre '79 351 into my '89 F250 and it's been very educational; v-belt vs serpentine belt, regular flow vs reverse flow water pumps and timing chain covers, dip stick locations...and now fan clutches. I've really learned a lot on this one.

Thanks for the help, guys.

 

No, No! Stupid me not good with English yet! The elements I spoke of are INSIDE the clutch, and direct the fluid flow; if one-directional design, I would hope some kind of marking exists on outside, but maybe not. The ribs on the outside are to help dissipate heat to the air, generated by the silicone fluid inside when it is thin and allowing the fan blade to "slip", thus generating heat, like a baby torque converter. impish

 

Please let me clarify this for a minute.

I had a '75 Ford F-150, 351. I had a flex fan on it, and when I let it go, I took parts off and stored them, one was a new flex fan. I then aquired my now baby Raven, and when the summer hit, I decided to take the good clutch fan unit off and put the flex fan on for more air movement while towing.
The direction of the blades weren't correct, but it bolted up fine on a 302. I removed it and put it back in the shop, where it sits in the origional box. I had to settle for a clutch fan system. A clutch fan system drive relies on the heat from the radiator, and ambient temp to activate a clutch to engage the shaft on the water pump system.
Going hiway speeds, will cool the system, while at idle, the fan kicks in.
I was never aware of 'directional' fan clutches, only engine rotation and blade direction. If, for any reason, confusion results from my reply I totally apologise, just going with my experience.

Regards,

 

Hey, no need to apologize for anything! We're here in this together, not against one-another! A couple of commonly-held beliefs about fans in general might be added. Lots of people think if you turn a fan blade around, but turn it in the same direction, it will blow the other way! Not So! Only thing there is, blades are shaped and curved in a way to get most efficient air movement, so turning one around might just reduce it's efficiency.

Another thing is flex fans. They blow hard at low speed, "flatten out" at higher speed, supposedly to save fuel driving them. Truth is, it takes lots of TORQUE to spin a flex fan fast enough to flatten it's blades out-- after all, it's a huge amount of air needed to force them down, right? Yes, at highway speeds USUALLY enough air is forced through the radiator by vehicle movement that a fan isn't even needed. Usually, but not always: such as when the engine is working hard as hell to keep up speed, towing, maybe, especially up a long mountain grade, where it's very hot that day. That's when a good fan is needed to add air flow to the stream passing through the radiator. So, personally, just my own opinion, understand, I don't particularly like flex fans. One good point in their favor is, they don't wear out and fail, like clutch fans do.

The old solid fans did the job, ALL the time, though. My 289 HP Mustang came from the factory with a 5-bladed, solid fan with weirdly uneven-spaced blades, got the job done, sure, but...

For me, a clutch fan is the best alternative. Lets fan blade spin idle when no added cooling is needed. In fact, it's the air coming through the radiator from forward movement which makes the blade turn slowly under those conditions. As the air temperature passing through the radiator goes up, to the point where added fan cooling is needed, the silicone fluid in the clutch "thickens" gradually, more and more, and drives the blade to move additional air as needed, then thins out again, as the air temp. drops, letting the blade slow down again. The premium clutches have a little coiled spring attached to the front of the clutch, about half-dollar size: That thing is a bi-metallic spring which "unwinds" as the air gets hotter and hotter. It's connected through a shaft into the clutch, and varies the angle of the blades against which the fluid is pushing, like the stator in a torque converter. Cheapie clutches often do not have this added feature; they rely solely on the fluid's viscosity change inside the clutch.

If one takes a minute or two, each time while doing the "underhood check", to grasp the fan's blades on opposite sides, and feel for play (sidewise movement), a failing clutch bearing, or water pump bearing, can often be detected before actual trouble develops. Both clutch fans and water pumps fail in the same way: the seal fails, allowing fluid to leak out, or the bearing fails first. Occasionally, the fan clutch bearing will fail by "seizing", then the blade is driven all the time, and is usually heard similar to a prop-type airplane going over! If the bearing fails by falling apart, or the watrer pump shaft breaks off, the possibility exists of the fan blade "screwing" itself into the radiator. The pitch angle on fan blades is such that if they contact the radiator, they dig into it, like a shovel.

Just my thoughts, as usual making a simple subject complicated! impish

Edit: Anyone with an avatar showing neat-looking girls is A-OK!!

 

I thought I might ask the group if anyone has ever run the flex fan with the fan clutch?
I am rebuilding my timing case cover after the water ports leaked.
I decided to "upgrade" my parts to a new 28oz chrome dampener, all new seals and gaskets and a new 18" flex fan reverse rotation for the serpantine belt setup.

My question is can I use both the flex fan with my existing clutch since the fan bolts directly to the clutch? I still have my old five blade for the clutch.

Any input would be appreciated

 

A clutch fan, is a solid blade fan, attached to a thermo-'clutch', which only operates when the temp of the clutch rises, it grasps the shaft firmer, and uses the rotation of the shaft to spin, cooling the system. At road speed, the temp lowers due to 'ram-air' and will dis-engage the clutch alowing the blades to free-wheel.

A flex-fan, has a fixed shaft to the pully system. The blades are made up of light grade steel or such that at high rotation, will flatten out. When engine speed decreases, the blades will return to the pre-curved design, pulling in more air.

To put a flex-fan on a clutch fan system would be highly counter productive to the clutch, and the pully system. Hope this helps.

P.S. Road tractors use a Horton Air clutch system, where the engine temp sends a signal to an air controlled fan clutch system, engaging the fan.