2.3L ('83-'97) Flex fan vs fan clutch

[bmtrnavsky]

I am tearing my motor down to do a head gasket on it so while it’s apart I’m doing a few upgrades just looking for a few HP and MPG I’m not building a race car here. So while the heads off I’ll magnaflux it, mill a couple thousands off and do a valve job on it. I’m also adding a high flow cat and cat back system and will probably gasket match my intake and exhaust. While I was removing the fan I noticed it’s in pretty rough shape... so I started researching fixed, clutch, flex, and electric fans. All have pros and cons and I discovered even the electric fan causes some parasitic loss and can also cause the engine to run too cool so I’m thinking a flex fan is the route I want to go. Best air flow lower high rpm resistance. Anyone else try this? All the Dynomax tests are on big block race motors and I’ve seen huge hp gains (3-5 wheel hp) I’m guessing our 4 cylinder is probably more hampered than a V8... any one tried it? What else have you done for MPG?

 

[RonD]

Never tried direct drive flex fan in place of fan clutch, so can't help there, but I would speculate a "working" fan clutch would be better for HP and MPG

But I would revisit the e-fan option

Fans are ONLY needed when driving slowly or stopped
Above say 35mph air flow thru rad is fine for cooling, and of course higher speed higher cooling

Classic symptom of failed fan clutch is temp gauge going up when stopped, then going back down when moving again, thats because fan is not really needed until stopped

So an e-fan wouldn't/shouldn't be on above 35mph, so 0 draw on alternator(or engine), it would only be on when driving slowly or stopped and you don't need extra horse power at those times, unless you are building a rock crawler, lol

As for running too cool, that's strictly up to your installation and how you setup the thermo switch and temp on and off for the fan relay, totally in your control

So it really is a win-win with an e-fan setup, better HP and MPG, few things can do BOTH

 

[Shran]

A fixed fan is going to hurt performance somewhat more than a factory clutch fan and significantly more than an electric one. The factory fan clutch is a really good compromise between cooling and efficiency, a quality electric fan with a quality fan controller that turns it on and off at specified temperatures is a close second only because it's costly and quite a bit more complex.

No way would I put a flex fan on one of these trucks.

FWIW my 4 cylinder truck almost never hits the thermal on the fan clutch.... ONLY on the hottest of the hot days.

 

[19Walt93]

I just put one of these on the 86 I'm building for a friend, it looks like a good piece and isn't noisy. I got it from Summit.

Derale High-Output Single RAD Fan and Shroud Kits 16816

 

[8thTon]

I never liked the idea of a flex fan - mostly they are aluminum I think, and aluminum always has a finite number of cycles to fatigue failure, unlike steel. So you've got this spinning fan that's constantly flexing and will ultimately break. Sounds like a bad plan.

 

[sgtsandman]

I never liked the idea of a flex fan - mostly they are aluminum I think, and aluminum always has a finite number of cycles to fatigue failure, unlike steel. So you've got this spinning fan that's constantly flexing and will ultimately break. Sounds like a bad plan.

I thought flex fans were always steel for the reasons you state. I could be mistaken though. I also thought, though I never ran one or seen one ran, that they were still attached to a fan clutch instead of being directly connected to the engine.

 

[8thTon]

I thought flex fans were always steel for the reasons you state. I could be mistaken though. I also thought, though I never ran one or seen one ran, that they were still attached to a fan clutch instead of being directly connected to the engine.

Ok, I could well be mistaken on the material.

 

[bmtrnavsky]

Is there a way to test your factory fan clutch?

 

[19Walt93]

A fan clutch saves power until it locks to drive the fan. In the late 80's we had a rash of failures on F trucks. I got a call from a customer who was travelling in the South and had broken down. He was at a dealer and they had been working on it for hours but couldn't find his power loss. He told me his 302 F150 wouldn't go over 50 and sounded like an airplane. The fan clutch was locked/seized. That's how much power the fan eats when the clutch engages. The power increase will be worth the price of an electric fan and the fuel savings will offset some of the cost,too.

 

[RonD]

Is there a way to test your factory fan clutch?

Yes
When engine is cold before starting open hood and try to spin the fan blades, should be tight, hard to move, its cold locked
Start engine, you should hear fan moving air then after 10seconds it will get quieter as it unlocks, in any case shut off engine after 20 seconds
Try to spin fan again, should be easy to spin, unlocked
If it spun easily cold and after 20sec run time then its bad, it can't lock

If it's not easy to spin then clutch is stuck, partially locked, its failing, could go full unlock or full lock, roll of the dice

After driving for 20-30 minutes, after temp gauge has been just below 1/2 for at least 10 min, shut off engine and test fan spin again, should be semi locked, harder to spin, really depends on Rad temp in the center


Fan clutch has a bi-metal spring on the front, that spring expands, uncoils, when heated by the RADIATOR, not the engine
So as radiator heats up in the center, in front of the spring, the spring close a valve inside the clutch causing it to lock
Lock means it spins closer to to water pump RPMs, and it variable based on the temp of the spring, so on the temp of the center of radiator
If you radiator has clogged tubes in the center....................then spring does get as hot

 

[bmtrnavsky]

Anyone have a budget guide on the correct way to go electric? I seem to remember you can get one off a explorer? But what parts do I need? How do I wire it?

 

[franklin2]

I agree with some of the others, I would not go flex fan. The reason being I have had one fly apart and stick in the hood insulation, and a guy I work with had his fly apart and ruined his radiator. These were the metal types, and yes they were aluminum blades. Someone said they make a all plastic version that holds up better, but I was done with them by then.

I am running a 16 inch local store bought fan on my BII. I had this same setup on my 86 ranger with the 2.9. I originally put it on the 2.9 because that factory plastic fan was all cracked up. And I happened to have this fan laying around. Then when I put the BII on the road, the radiator was bad in it, so after some modification I put the 86 ranger radiator/fan combo into the 84 BII. In both cases I recommend using this size fan if you go with the cheap versions (I say cheap but it was $75 for the fan). Two of them did not move enough air for my diesel pickup, but one of them seems to be just right for these little v6's.

The control I use is the cheap one at the store, it works good, and has been working for the past 5 years. It's one of these

I wire it directly to the battery. Then through the switch and then to the fan. The only problem is the temp probe. They want you to slip it up into the upper large radiator hose, and run the small wire out and clamp around it. It's very difficult to keep this from leaking. So I put this setup in one of the heater core hoses.

Electric fan probe by D Franklin, on Flickr

P.S. If you are running A/C you MUST add a relay to bypass the temp control and run the fan anytime the compressor is running. Big things happen under the hood if you don't. Been there, done that.

 

[PetroleumJunkie412]

American Volt temp sensor (thermostat) in the LOWER rad hose.

I've been through all of the rest of them, all have failed in one way or another. American volt thus far is as close to indestructible as I can find, and may not need a relay depending on power draw from the fan.

Plus, made in the USA.

 

[RonD]

Anyone have a budget guide on the correct way to go electric? I seem to remember you can get one off a explorer? But what parts do I need? How do I wire it?

Good page to have Bookmarked here: https://www.therangerstation.com/tech_library/index.shtml

Look in the Cooling and Heating section, there are a few E-Fan articles by members


Basically you need a fan and shroud that fits you radiator
A relay rated for the amp draw of the E-fan motor
A temp-switch, so YOU can decide when fan comes on and when fan goes off

 

[Fredness]

Ah flex fans...
...and the myths.

It must be made for a "serpentine" system (to spin the right way), you want a QUALITY blade (not cheap), and stainless steel if you can find it.
The fan would need a quality spacer to put the blades IN the shroud, but away from the radiator (measure the factory set up and mimic).
I've been running a stainless flex fan for over 10 years with ZERO mechanical issues.

Down sides:
They are sharp, there will be blood.
Increased noise at idle from moving air.

Up sides:
More airflow at low RPMs and idle, in TX it's nice to have AC at a long light!
Slight mpg bump.
Slight hp bump.
No cooling issues.
Dropped more than 3/4's weight off the nose if the waterpump.