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  #1  
Old 10-06-2012, 01:07 PM
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Miraphone186 Miraphone186 is offline
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Electric vs Mechanical fan

Hey guys, I was installing the new radiator in my G wag and the shroud for the mechanical fan broke in two when I was removing it. This got me thinking, I could get another fan shroud, or maybe I could buy an electric fan from bjs and bolt it in. After some research, it seems that mechanical fans cool better on the highway, while electric fans do better at low speeds, and because I'm going to be going on both the highway and doing some low speed offroading which one would be the best overall? I've also considered running both, but i'm not sure if they'll interfere with each other or not.
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Old 10-06-2012, 01:17 PM
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Tinkerjeep Tinkerjeep is offline
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you will likely not fit both an electric puller fan and the mechanical fan. You can mount a pusher fan in front of the Rad...but you probably have a bunch of other coolers and crap up front already.

Which is better? For efficiency -the stock mechanical fan. it requires no wiring, no fuses, no relays , no temp switch and does not pull charging load from the alternator. No special mountings etc.

I ran dual electric fans (not sure what they were out off) for a few years and finally got tired of the noise and electrical draw on the 140 amp Alternator at idle when running in extreme cold, with defroster, headlights, heater-fan motor at full-on and wipers on...at idle. Its too much amperage draw and the belts would slip, squeel.

You could maybe pull it off if you don't run alot in cold/dark/wet situations.

I'd try to get a shroud and just run the stock mechanical fan. It works great when the clutch is working properly.
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Old 10-06-2012, 01:38 PM
joe joe is offline
 
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This'll prolly turn into a mech-vs-elec piss'n match but I'm a firm believer in steel solid mounted(no clutches or silly flex stuff) fans properly spaced under the shroud. If your cooling system is clean and in good condition with the proper coolant you don't need electric band-aids. If replacing the radiator I always toss in a new pump at the same time. Get your cooling system back to stock spec, then maintain it, flush swap in fresh coolant every two years and your golden. I don't rock crawl but worked the summers (geology) in AZ, NV, ID, OR, UT etc deserts with lots of slow speed low gear use and never had a cooling issue. Yeah a solid mount mech fan is a perceived HP drain but I don't run 4000 lb 4x4's at the drag strip so I don't care about HP numbers.
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Old 10-06-2012, 01:57 PM
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Joe's right in one regard -removing the clutch does remove a potential complication...but its there for a reason.

most of the non-clutch mech fans I've seen are four bladed. Jeep fans are 7 bladed...

but pick your poison.
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Old 10-06-2012, 02:11 PM
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Joe has good points

It clearly depends on what you do. Fans have no use at highway speeds. Your HP drain is minimal. Electric fans a band aid? I wouldn't say that although I don't use one. I still have the clutched system. It works fine. Been a lot of great write ups about fans. If you don't have a perfect system it really doesn't matter. Mine doesn't have a shroud either. Probably not recommended but it works fine. I like the guys that set up pusher @ about 225 degrees come on for back up. That can not hurt. But that is just me. If I were to run pure electric I would run 2. Not 2 small ones, 2 that would operates the vehicle with one working. My standard fan with the clutch has never let me down so I've never gone there. I do have to agree the main reason I haven't is because of the electrical clutter. Out in the middle of nowhere more complicated isn't good. Then again that may not be your game.
Figuring out what you want to do is half the answer.
I really don't understand that belt squealing issues on a 140 amp alternator. Obviously something else is wrong tons of vehicles are running fans on 80 amp system & less. A properly engineered systems wouldn't have issues like that.
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Last edited by serehill : 10-06-2012 at 02:13 PM.
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Old 10-06-2012, 05:23 PM
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Ok how about this. I have run both. Once with electrics to see if it really helped, once as a band-aid. And the stock mechanical with the stock clutch and severe clutch. I will tell you this, if your going to run electrics, even the cheapie Ebay ones like I did, you need to make sure your electrical system is up to it. So price of the fans, making a shroud, upgrading alternator and wiring, relay and wiring for fan. Making 100 hp more? No. And your out $300 that you can use for lighted tire valve caps. Severe duty clutch, barely stop turning, very loud and annoying to me. I don't have a quiet stock truck. $65 for clutch. You have a new radiator. Are you fighting an overheating issue, or is your stock one done. I have an aluminum radiator, with the stock clutch and I can't get up to full temp. Get it now? spend the $50 for another shroud and be done with it. This comes form a guy who SWORE the stock cooling system couldn't do the job.
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  #7  
Old 10-06-2012, 07:26 PM
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On a future build I'm looking to go electric, but that is because I'm using a 4.3 GM engine and the shroud would have to be a large most likely custom piece to work with a mechanical fan... and I don't want to hear the laughter over putting a 4.3 in a FSJ, I'm using what I have (Wife's old DD S-blazer) and building a J-cab something maybe even on a Wag frame for my oldest Son who will be old enough to drive in 3 years, don't want a first vehicle with a ton of power either.
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Old 10-06-2012, 08:18 PM
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Quote:
Originally Posted by joe
This'll prolly turn into a mech-vs-elec piss'n match but I'm a firm believer in steel solid mounted(no clutches or silly flex stuff) fans properly spaced under the shroud. If your cooling system is clean and in good condition with the proper coolant you don't need electric band-aids. If replacing the radiator I always toss in a new pump at the same time. Get your cooling system back to stock spec, then maintain it, flush swap in fresh coolant every two years and your golden. I don't rock crawl but worked the summers (geology) in AZ, NV, ID, OR, UT etc deserts with lots of slow speed low gear use and never had a cooling issue. Yeah a solid mount mech fan is a perceived HP drain but I don't run 4000 lb 4x4's at the drag strip so I don't care about HP numbers.

X2. I have rock crawled in lo-range in desert heat and never had a problem, and it was because stock radiator, fan clutch, shroud, pump & coolant were all up to snuff.

Also, you'll have an HP drain whether its an e-fan or mechanical. When the alternator is working harder to supply the extra current, it has an increased mechanical resistance that the engine feels through the belts. When you spin an alternator by hand on the bench you feel no resistance. But when its in place, hooked up and loaded down, there's plenty of resistance.
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  #9  
Old 10-07-2012, 01:01 AM
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I couldn't care less about horsepower drain, I'm just having issues with cooling when I'm sitting. If I sit long enough the temps just go up and up and up until it overheats. It did this before with the crusty old stock rad too. The water pump and fan clutch seem to be good, but maybe not. I'll check it out tomorrow.
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  #10  
Old 10-07-2012, 03:04 AM
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Factory cooling system with everything in good condition, should be fine. That is the key here, is everything in good condition?

To me (off-roader) the biggest reason for electric fans would be for water crossings so I can shut it off. Run a stock fan in deep enough water it will try to eat the radiator, not to mention bending the blades a lot of times.

Another place they are useful is for other coolers mounted where the stock fan dont pull air across them.




Back to your heat problems....

If your cooling system is OK, check to be sure your engine isn't running lean. An engine that is running lean will generally produce more heat, and can contribute to overheating.

Jim
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  #11  
Old 10-07-2012, 06:19 AM
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Thats what I'm getting at. Let's get the to the bottom of this. Motor specs? Replace T-stat? Flush system?
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  #12  
Old 10-07-2012, 06:57 AM
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Count your fan blades, there should be 7. The DPSO had put a 6 blade fan on mine. It was fine if I was moving, but sitting traffic, it would slowly creep up temp till it overheated. The fan blades should also be cupped, not flat. I had replaced EVERYTHING in th cooling system, and the timing and carb were perfect. And it still overheated. After changing the fan to a 7 blade, it will barely get to a proper operating temperature.
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  #13  
Old 10-07-2012, 07:00 AM
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There's some very good reading here:

http://oljeep.com/rad/edge_radiator.html
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  #14  
Old 10-07-2012, 03:46 PM
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Quote:
Originally Posted by serehill
I really don't understand that belt squealing issues on a 140 amp alternator. Obviously something else is wrong tons of vehicles are running fans on 80 amp system & less. A properly engineered systems wouldn't have issues like that.

0F degrees, hard rubber belts and idle speed.sitting at a stop, waiting for traffic after just starting the truck with no block heater...so the cold cranking added up. plus a 140 amp alt doesn;t charge 140 at idle...especially if idle is 700rpm or less.

I'm not sure what amperage draw my dual side-by-side fans were, but running two of them off the alt output post through twin 30 amp fuses and twin 30 amp relays to a common switch just to be safe... anyway...they just added complication and load to a cold battery/alternator. They cooled real well when I remembered to turn them on!

I do not have a fan shroud on any Jeep I own (they all broke and I never could find cheap replacements... I thought the factory ones were crap anyway. I plan on running one in the 401 J4X truck someday, but I'll fab it out of thin Aluminum most likely.

Right now the 401 does not overheat...but I have no AC or anything in front of the rad, and I don't go crawling in low gears in the desert. Haven't done any real off-roading for a long time, in this truck. Gotta fix a balljoint and get my new tires on before I do any again.
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Old 10-07-2012, 05:05 PM
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Interesting

Quote:
Originally Posted by Tinkerjeep
0F degrees, hard rubber belts and idle speed.sitting at a stop, waiting for traffic after just starting the truck with no block heater...so the cold cranking added up. plus a 140 amp alt doesn;t charge 140 at idle...especially if idle is 700rpm or less.

I'm not sure what amperage draw my dual side-by-side fans were, but running two of them off the alt output post through twin 30 amp fuses and twin 30 amp relays to a common switch just to be safe... anyway...they just added complication and load to a cold battery/alternator. They cooled real well when I remembered to turn them on!

I do not have a fan shroud on any Jeep I own (they all broke and I never could find cheap replacements... I thought the factory ones were crap anyway. I plan on running one in the 401 J4X truck someday, but I'll fab it out of thin Aluminum most likely.

Right now the 401 does not overheat...but I have no AC or anything in front of the rad, and I don't go crawling in low gears in the desert. Haven't done any real off-roading for a long time, in this truck. Gotta fix a balljoint and get my new tires on before I do any again.

That's what I thought it still sounds like something wasn't right. I've got a mustang with dual fans & the alternator does not pump out 80 amps at idle either. I've seen it idle 45 minutes with both fans no problem. They both run perfectly at idle with ac on which is drawing max amps without squeal. I don't think there's anything wrong with electric fans but the subject was if your doing it because your standard cooling suystem ain't cuttin it something is wrong.
I don't run a shroud either but I do run an aluminum radiator. I totally agree you can't run electrics with the stock system forget it.
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Old 10-07-2012, 06:11 PM
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Quote:
Originally Posted by serehill
That's what I thought it still sounds like something wasn't right. I've got a mustang with dual fans & the alternator does not pump out 80 amps at idle either. I've seen it idle 45 minutes with both fans no problem. They both run perfectly at idle with ac on which is drawing max amps without squeal. I don't think there's anything wrong with electric fans but the subject was if your doing it because your standard cooling suystem ain't cuttin it something is wrong.
I don't run a shroud either but I do run an aluminum radiator. I totally agree you can't run electrics with the stock system forget it.

I don't know if something is wrong or not. But I pulled the fans off and reinstalled a stock fan unit. it works fine now and the relays/fuses are only used on my 55Watt driving lights, which are rarely used. The Alt voltage regulator crapped out shortly after that and wouldn't charge unless the motor was revved up to 2k RPM . I took it to the shop to have it rebuilt...whenever he gets around to it. that was a few months ago. I'll see what it does when I get it back in the truck.

BTW. I think my belts are like 6 years old now...they were 3-4 years old then... and cold hard rubber belts don't grip well...maybe that was part of it too...?
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Old 10-07-2012, 06:16 PM
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That explains a lot

Quote:
Originally Posted by Tinkerjeep
I don't know if something is wrong or not. But I pulled the fans off and reinstalled a stock fan unit. it works fine now and the relays/fuses are only used on my 55Watt driving lights, which are rarely used. The Alt voltage regulator crapped out shortly after that and wouldn't charge unless the motor was revved up to 2k RPM . I took it to the shop to have it rebuilt...whenever he gets around to it. that was a few months ago. I'll see what it does when I get it back in the truck.

BTW. I think my belts are like 6 years old now...they were 3-4 years old then... and cold hard rubber belts don't grip well...maybe that was part of it too...?
I do have to say though I'm a fan & clutch guy.

I suppose I should get back to Miraphones question Just get the shroud.
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Old 10-07-2012, 06:33 PM
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Quote:
Originally Posted by mrtazwrench
On a future build I'm looking to go electric, but that is because I'm using a 4.3 GM engine and the shroud would have to be a large most likely custom piece to work with a mechanical fan... and I don't want to hear the laughter over putting a 4.3 in a FSJ, I'm using what I have (Wife's old DD S-blazer) and building a J-cab something maybe even on a Wag frame for my oldest Son who will be old enough to drive in 3 years, don't want a first vehicle with a ton of power either.
Where is the build thread at? I want to check this out when its done!!! My dad had a 4.3 s10 and that thing pulled HARD for a 6 cyl, plus sbc stuff just bolts on since its a 350 with 2 cylinders cut off!!! Sorry for going off the topic of the thread
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Old 10-07-2012, 06:55 PM
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Quote:
Originally Posted by serehill
I do have to say though I'm a fan & clutch guy.

I suppose I should get back to Miraphones question Just get the shroud.

I think we're all good...on topic. it all contributes to the general knowledge base: our experiences.

He may not do it the way either one of us did...and still have problems...or have none...

I know stock AMC/Jeep stuff from the 1970s was pretty much engineered to work...as long as the stuff is maintained. The later stuff built in the 1980s: the engineers seemed to skew away from durability and preferred light-weight or hands-off functionality for improved "luxury/mileage"...the new Jeep owner mindset. AMC was not the only manufacturer to suffer from this abberation...but then...they subcontracted most of their parts out from...GM/ Ford/ Chrysler...who all went lightweight/mileage-friendly/ weak in the 1980s So AMC was stuck.

I say...if you notice the temp gauge rising...or the overflow tank is puking...shoot a temp gun at various bits of the engine...

Radiator top-tube temps should be no more than 205...lower tube should be at least 20 degrees cooler than upper. that indicates a properly working cooling system... ifyour Jeep runs hotter than this...find out why and fix the source...the fan is only one small part of the equation.

And don't start drilling holes in the hood to promote cooling...THATS a band-aid.
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Old 10-08-2012, 12:17 AM
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if necessary there are some fairly affordable mechanical upgrade options that work really well with fsj's if you are wheeling alot or living in the desert with AC on and/or something in tow this might be helpful.


This all came about from a little time in the desert, nor cal towing alot in the hiils with extremely hot weather (100-105+) and wheeling alot. Even with a well maintained stock rig you find the short comings of some of jeeps designs. Ford, dodge and GM all later on offered the ambulance, desert packages or severe duty cooling packages, especially after diesels and heavier towing became common place in the 80's 90's and beyond the catch is jeep esentially didnt change anything cooling wise on our beloved FSJ's after 1972.

a little modern day technology & parts upgrades that easily fit for less than $140-160 all said and done that make a noticable difference might be worth considering, but arent necessary for every one



After some research im of the opinion that the stock fan for its diameter it should have more pitch and displace more volume than it does but the flatter design with less pitch result in s less air noise. it works in stock applications driving down the road but if you start working the rig the short comings of some of amc's design show up.

Also the fan clutch, as things have progressed there are heavier duty models developed that will provide more lock up. many modern day or replacement hayden etc fan clutches are set to fully engage at a higher temp than we all would like. this is done for emissions. thing is fan clutches are adjustable so ive also attached an article here that will help.



heres my .02 worth of mechanical upgrades that have worked well.
(i use a pusher fan in some applications as a suppliment in rare occassions, mechanical setups should be able to keep things cool, electrics are imho a bandaid. in my case i was doing alot of lugging around at extreme low speeds 500 rpm and generating alot of heat on hot days and a pusher fan was ideal in that situation to help increase volume of air at the low speeds otherwise im not a big fan of electric fans)

With a really well setup rig running a nice new 4 core radiator, good thermostat and new fan clutch on stock fan with factory shroud towing and wheeling with a 401, AC and a 4 speed i discovered that my jeep had some short comings in hot weather that the factory cooling system setup sometimes just barely could address. (mechanical gauges tell alot more than guessing on an idiot gauge) robbing a few tricks from more modern severe duty applications are a way to get that little bit of an edge and make up where jeep left off and quit caring without having to spend a fortune on aluminium radiators and adding electric fans


How it all started:
as a simple test at the onset i paid $5 at the wrecking yard for a higher pitched fan.

I can tell you that i swapped out the factory 7 blade 19" fan and the replacement was an 18" sourced from a caddilac with a 472/500. 18" in diameter, 7 blades with 3-1/8" of height and 38 or 39* of angled pitch vs the factory 19" with 2" of pitch which iirc was something like 27-28* of pitch. BIG difference in the amount of air noise and air pulled through the grille when locked up. another option that i used in the end is the 10 blade hummer diesel fan 19.5" fits a stock fsj shroud. towing alot in 100 degree weather in the foothills of CA on slow dirt roads taxed what the stock fan was capible of.


For cooling fans:
Fans from a Cadillac el dorado running a 472 or a 500 are 18" in diameter and 3-1/8" high pitch 7 blade blades are 5" across by nearly 5" long found this to work well even with the stock fan clutch. it had no problems keeping my motor cool and moved as much air if not a little more than the stock fan based ont he amount of dust being kicked up from under the rig after the swap vs before.

another fan that fit worked as well if not a little better was the hummer fan, downside is it was $110 but it was designed for some of the most extreme conditions to suck the maximum amount of air and it does work well heres a link to the hummer fan 19.5" and 10 blade
the fan is 19.5" in diameter the blades are 6-1/8" long 3.5" wide and have a 2-1/8" high pitch so also IIRC 38-39* pitch


Fan clutch PN#
For an improved range of operation with mechanical cooling the stock clutch has its limitations it only rotates at 60-70% of shaft speed meaning you are passing on some air. Using a 82-86 buick diesel severe duty fan clutch is a help. it fits the stock water pump and clears the radiator, i cant say enough about a really good severe duty fan clutch over the stocker. it came about with the evolution of diesel engines and the development of ambulance applications, plaes where extreme heat and tight trapped engine compartments became a problem stock 60-70% lock up vs 80-90% lock up with a severe duty is a big help. Hayden Part number 2797 watch out some from napa arent slotted so you'll have to cut them the ones from summit are slotted and fit our water pump studs no issues


How much of a difference I dont know
now im no fan specialist but best i can tell the 472 cadilac fan blades account for 25 cubic inches each x7 would yeild 175 cubic inches of surface area. the military diesel 92-94 hummer fan accounts for 21.4" of surface area per blade at 10 blades would yeild 214 cubic inches of surface area. best i can tell the hummer fan which will bolt up to the 2797 fan clutch pulls more air than the stocker for sure and a touch more air than the caddy fan. you can use the 2797 fan clutch with your fan especially if yours is shot but if you are in there doing the work id think long and hard about putting a hummer fan or some other higher pitched fan in there while replacing things. i wouldnt at the least upgrade to the severe duty 2797 fan clutch when you replace your fan clutch


Adjust your fan clutch.
Also on fan clutches all replacements out there like to engage between 210-220 here is an article discussing this and how to address high engagement settings on factory thermostatic fan clutches and adjust them to get them to engage at lower settings you'll be amazed at the difference. mine now engages nearly fully at 180*. excessive or constant high temps under the hood contribute to the deterioration of hoses and belts as well as lean run.

Thermostats
remember to run a robbert shaw or MR gasket quality thermostat and not a cheapo unit, 180* is what i run now and it sticks there even in 100* weather. i used to run the 195 but preffer the 180, my temps are more stable and the engine appears to run better.
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Cherokee S Chief Widetrack W/ Cummins 4bta Diesel, 91 dodge intercooler, hy35/9, AC NV4500/D300 3.54's Ploks 4" BJ's w/ 33's, scout 33 gal fuel tank ( Sold, to a good fsj home)
The 608.9 hybrid dana 44 build

AMC 401 supporter

GO UM Montana Griz

"Dont worry the Coors light engineering department will be documenting this accordingly."

Last edited by dusty : 10-09-2012 at 08:26 PM.
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