Stock electric cooling fan - keep it or replace it?

[Number21]

I want to install electric fans on my '98 XJ. I know there are a million different ways to do this and just as many opinions on the subject. I have seen people get rid of the stock electric fan and replace it with three aftermarket fans, and I've also seen people keep the stock fan and use either one large fan or two smaller ones to replace the mechanical fan.

My question is, is there anything wrong with the OEM fan on a '98? Will an aftermarket fan move more air, or is the stock one good enough? (it sure fits nicely!) I know they made various upgrades to the stock fan throughout the years, but I think the '98 is one of the better ones, is this true? Would I get better cooling if I replace it with a different aftermarket fan?

 

[David_Bricker]

Please search the forums, as you will find a number of threads discussing electric fans. Invariably, the answer comes back that the best fan setup is the stock mechanical fan with standard ZJ fan clutch, and a 97+ electric auxiliary fan.

Bottom line, there is *no* 10" diameter electric fan that will pull as much air as the stock mechanical fan.

Now, in North Carolina, where there is a lot of humidity, and it's not 120 degrees, you "might" get away with high end electric fans. In Death Valley, the electrics just can't cut it.

David Bricker / SYR

 

[Jeep Driver]

I had to change two freeze plugs in my Kubota today.


Years ago, in another truck I had, I had the Efan wired live. When I shut the engine down, the fan would cycle through several times in about an 8 minute period. I never really understood what was happening until I got a diesel tractor.

I'm posting this for those who have, or believe they have, heat soak, or for anyone else that want's be become creative with their Efan.

Once you shut your engine down, the coolant continues to flow, your thermostat continues to open and close until siphoning no longer takes place. I'm guessing, somewhere between 150 and 160 degrees.


Many tractors, machines, and other industrial equipment rely solely on thermsiphoning as a means of cooling. My Kubota, for example, does not have a water pump.


Just something to think about for those who want to take advantage of what is naturally happening anyway. By the time you run into a 7-11, fill your Big Gulp and pay for it, your temp should be down around 130 degrees with a live Efan.

https://en.wikipedia...ki/Thermosiphon

kL1Oh1gh.jpg

And I will disagree entirely with the 2nd post.

Above is a post I made yesterday elsewhere........just one aspect of Efans.


Efans get a bad wrap because 90% of the folks that try them don't know how to mount them, how to choose them, how to wire them.

 

[David_Bricker]

I can only post from my personal experience. Three 10" electric fans, with or without shrouds did not cool me sufficiently. Switching back to stock mechanical and electrical fans did. I spent a lot of hours with the radiator and fan supplier to no avail.

I've also spent a few hours talking to the Griffin techs, and they tend to agree, despite them selling an electric conversion, in my case the mechanical fan will pull more CFMs.

While quite interesting, I'm not sure what thermosiphoning has to with electric fans, other than an electric fan can run when the engine isn't running. To this conversation, that isn't a discussion point. It may help with heat soak, but that can be accomplished by putting a time on the stock electric fan.

It would interesting to know whether thermosiphoning occurs to any great extent in a 4.0L motor. The presence of a water pump would tend to hinder that. On your Kubota, I'm guessing the system is designed to flow different than our Jeep motors.

David Bricker / SYR

 

[Jeep Driver]

I can only post from my personal experience. Three 10" electric fans, with or without shrouds did not cool me sufficiently. Switching back to stock mechanical and electrical fans did. I spent a lot of hours with the radiator and fan supplier to no avail.

I've also spent a few hours talking to the Griffin techs, and they tend to agree, despite them selling an electric conversion, in my case the mechanical fan will pull more CFMs.

While quite interesting, I'm not sure what thermosiphoning has to with electric fans, other than an electric fan can run when the engine isn't running. To this conversation, that isn't a discussion point. It may help with heat soak, but that can be accomplished by putting a time on the stock electric fan.

It would interesting to know whether thermosiphoning occurs to any great extent in a 4.0L motor. The presence of a water pump would tend to hinder that. On your Kubota, I'm guessing the system is designed to flow different than our Jeep motors.

David Bricker / SYR

Every engine thermosiphons, that was the point.

Live, meaning, though direct wire or delayed timer.............fast cool down after shut down.



I'm not a teacher, not my job, don't care for a shit fest either........not the point of my post.

My point was to get people to think.



I have a new engine that only has about 7 hours of run time that has yet to see 200 degrees.



Way too many variables here to give a strict and direct answer to anyone, you must do your own research and trial and error.


For example, did you drill 1.5" hole at each corner of your shroud?
This may seem counter intuitive, however, shrouds actually create turbulence which in turn creates hot spots, the fan is not drafting the corners. 30% of your rad is not only NOT cooling, but getting hotter. The holes actually allow air to flow and relieves the turbulence.


Thermostats seems to always be a problem, where you place your thermo switch and at what temp it comes on...........and so forth..........


Efans need to get ahead of the heat, not try to play catch up.

This is the best switch I have found, it simply works-

 

[Number21]

And I will disagree entirely with the 2nd post.

Me too. Yes, I've seen the millions of electric fan arguments. That's why I didn't ask if I should use them or not. I'm not asking if it can be done, I'm not asking if I should do it. The only question I asked is, is the OEM electric fan good or is there something better available?

For example, if I had a 1990 model year, the 1997 OEM fan would be an upgrade. That is still 20 year old technology. Did they improve the fan any further after 1998?

I *WILL* be replacing the mechanical fan with an electric one, the only question is should I leave the other side alone or put something better in.

And yes, one of my reasons is to install a timer to allow the fan to run after the engine is shut off. Probably an auxiliary electric water pump also...

 

[Green XJ Jeep]

You can pull adequate air with 2 97+ e fans but they draw a lot of amps and negates the benefits of going electric.

The only reason to ditch the mechanical fan is for some reason the parasitic drag caused by it bothers you to that extent. You will not find an e fan that will fit that can out perform the mechanical setup in moving air.

As for thermosiphoning, it only happens until the thermostat closes. If water cant freely circulate it cant thermosiphon. At that point all you are doing is cooling the coolant that is sitting in the radiator and helping move hot air out of the engine compartment.

But its your Jeep knock yourself out. As said earlier it will probably work fine in your area.

 

[Number21]

You can pull adequate air with 2 97+ e fans but they draw a lot of amps and negates the benefits of going electric.

I suppose you're an expert on this huh? Ever dyno it? Ever realize the mechanical fan is not needed at all during warmup or highway driving? Did you know the mechanical fan never turns off entirely...and even if it did there is still a large mass from the fan clutch? Did you know electric fans allow the engine to warm up faster causing less wear, and, less fuel consumption? (less time in open loop mode) Did you know the electric fans are more efficient, meaning, they perform the same amount of work with less load on the alternator? If electric fans are not better then why do most newer vehicles come equipped with them?

Or here's a big one...since I have two big deep cycle batteries, my alternator is normally switched off, thus entirely relieving the engine of that load. :scared:

I still notice nobody has bothered to answer the question I actually asked. I never asked if electric fans work or have any benefits...

 

[Jeep Driver]

I suppose you're an expert on this huh? Ever dyno it? Ever realize the mechanical fan is not needed at all during warmup or highway driving? Did you know the mechanical fan never turns off entirely...and even if it did there is still a large mass from the fan clutch? Did you know electric fans allow the engine to warm up faster causing less wear, and, less fuel consumption? (less time in open loop mode) Did you know the electric fans are more efficient, meaning, they perform the same amount of work with less load on the alternator? If electric fans are not better then why do most newer vehicles come equipped with them?

Or here's a big one...since I have two big deep cycle batteries, my alternator is normally switched off, thus entirely relieving the engine of that load. :scared:

I still notice nobody has bothered to answer the question I actually asked. I never asked if electric fans work or have any benefits...

If you can pick up one or two (matching) late model fans for $20 each, I'd try that route first.

SPAL high performance fans are the only ones I have found to perform, they are not cheap.


And, you are right, and that is the point of an Efan, for the Efan NOT to run most of the time.


If any of you are members of Motor Trend on Demand, check out Engine Masters, they did a mech fan dyno test, you'll find that interesting.

 

[Green XJ Jeep]

I suppose you're an expert on this huh? Ever dyno it? Ever realize the mechanical fan is not needed at all during warmup or highway driving? Did you know the mechanical fan never turns off entirely...and even if it did there is still a large mass from the fan clutch? Did you know electric fans allow the engine to warm up faster causing less wear, and, less fuel consumption? (less time in open loop mode) Did you know the electric fans are more efficient, meaning, they perform the same amount of work with less load on the alternator? If electric fans are not better then why do most newer vehicles come equipped with them?

Or here's a big one...since I have two big deep cycle batteries, my alternator is normally switched off, thus entirely relieving the engine of that load. :scared:

I still notice nobody has bothered to answer the question I actually asked. I never asked if electric fans work or have any benefits...

OK we will try this again.
Yes the 97 up are fine but they draw more amps than an aftermarket fan.
Probably still not a good enough answer for you but have fun with your project

 

[Number21]

If any of you are members of Motor Trend on Demand, check out Engine Masters, they did a mech fan dyno test, you'll find that interesting.

Is this the video you are referring to?
https://www.youtube.com/watch?v=ZXdLgaFXZzs

With a clutch fan on a regular old 350 SBC, it ate up 14hp while cold. That's a larger fan than an XJ has, but, not by a lot. On the other hand, as they pointed out, if your electric fans draw 30 amps continuous, that's about a 1hp drag on the alternator. (30 amps x 13.5 volts = 405 watts, alternators are about 60% efficient, and one horsepower = 746 watts)

I'll agree the belt driven fan moves more air, but do you really need all that air, all the time? I sure don't. The mechanical fan in an XJ is using 1960s technology. The "experts" conclude that electric is definitely the way to go.

Sucks when facts get in the way of a good story, huh? :shhh:

 

[burntkat]

Efans get a bad wrap because 90% of the folks that try them don't know how to mount them, how to choose them, how to wire them.

Convective flow is certainly a concern. I don't think that one needs to keep their fans wired hot when ignition is off, though. I have a 350 in an s-truck and they are switched to ignition, never had a problem.

The biggest concerns with cooling fans come down to CFM. How many cubic feet a minute do they move? That's the biggest thing to worry about. Absolutely you need a shroud, and to have a good seal around the shroud and radiator so that all the air MUST go through the radiator. But no matter how tight your install, if you're running a fan that flows less CFM, it WIL NOT cool the engine as well. Period.

I'd like to see some CFM data on the mechanicals versus a given candidate electric fan before I made the choice.

I am using two fans and the OEM shroud from a Dodge Intrepid on my S10 with V8 and it cools extremely well. There is no mechanical fan in this arrangement, and I had cooling issues until I went to this setup. Some folks with similar builds use Taurus e-fans with good luck. I could squeeze one in but it wouldn't fit my radiator as well as the Intrepid fans do- they fit my radiator like they were made for it after a little bit of contouring and application of foam tape. Additionally, the Taurus fans have ahigh inrush current- about 70A- and that presents issues for finding a good controller. The controller I built for my build consists of a BMW dual-temp switch and two 40A relays. Works just fine.

The specifics of that build don't apply directly to the XJ, mainly because of the odd shape of the radiator. But the principles are the same. It all comes down to airflow management, and CFMs.

 

[burntkat]

curs to any great extent in a 4.0L motor. The presence of a water pump would tend to hinder that. On your Kubota, I'm guessing the system is designed to flow different than our Jeep motors.

David Bricker / SYR

The proper term is convective flow.

It happens in all motors, regardless of a water pump or not. Basically after shut down the cylinders are still hot (although not getting any hotter, obviously).

The water isn't flowing, the radiator is still radiating. The water in the radiator cools off, the water in the engine up against the cylinders is still hot from the iron in the cylinders leaching off their heat to it. The water in the engine gets heated as the engine cools, and there is now a thermal gradient between radiator and engine. Hot water and cool water want to lay in layers ("thermoclines" for those of a Naval bent) and so flow occurs. It all has to do with convection.

I am not convinced it's a huge concern. There is no additional heating occuring to the engine, and the radiator will do its job whether or not there is air being forced actively through it. I always wire my fans to switched ignition mainly out of concerns for having a dead battery when I get back to the truck- 40-70A inrush current/30-40A steady state current is no slouch when it comes to running a fan. Plus, having the fans running when not driving the truck messes with alarm current sensing- making the alarm go off all the time. No thank you!

 

[burntkat]

I suppose you're an expert on this huh? Ever dyno it? Ever realize the mechanical fan is not needed at all during warmup or highway driving? Did you know the mechanical fan never turns off entirely...and even if it did there is still a large mass from the fan clutch? Did you know electric fans allow the engine to warm up faster causing less wear, and, less fuel consumption? (less time in open loop mode) Did you know the electric fans are more efficient, meaning, they perform the same amount of work with less load on the alternator? If electric fans are not better then why do most newer vehicles come equipped with them?

Or here's a big one...since I have two big deep cycle batteries, my alternator is normally switched off, thus entirely relieving the engine of that load. :scared:

I still notice nobody has bothered to answer the question I actually asked. I never asked if electric fans work or have any benefits...

LOTS of misinformation in this post. I'm laughing....

 

[Number21]

LOTS of misinformation in this post.

Do tell.

 

[lazyxj]

I can only post from my personal experience. Three 10" electric fans, with or without shrouds did not cool me sufficiently. Switching back to stock mechanical and electrical fans did. I spent a lot of hours with the radiator and fan supplier to no avail.

In the 14 years I have been on , many have here in the hot south-west have tried electric fans...and have gone back to the stock mechanical fan.
No electric fan, that fits, can pull the amount of air that the stock mechanical fan does.

Like David, my XJs run coolest with the stock fans, Mopar HD radiators, along with large coolers for the steering and transmission.
I have a shed full of used radiators and electric fans, tried unsuccessfully in the past.
Even if you can make the electric fan work, I have a problem with the added complexity and stress on the electrical system, there is so much more to go wrong, usually twenty miles from pavement.
I would worry about the stressed alternator dying on a hot day.
The stock mechanical fan has been proven to be dependable, as long as the fan clutch is changed every few years.

 

[burntkat]

Well first of all- you seem to think that having big batteries relieves the alternator of load. Uh, nope. Your batteries do exactly nothing while the truck is running. The alternator runs the show. You can quite literally disconnect the batteries entirely, and the engine will continue to run until it's out of fuel.

Temperature is only a small part of the time spent in open loop mode. So much so that the electric/mechanical fan issue is mostly a non-issue.

Then you contradict yourself in saying that "the mechanical fan is not needed at all during warmup or highway friving.. then turn around and say "the mechanical fan never turns off entirely. The latter part is true. While the majority of the cooling IS done via ram-effect while driving (ie, the fan isn't needed to suck air through as it's being forced through as the vehicle moves through the air) it's not ture to say the fan isn't doing anything while at speed. This is even more true during warmup.

Concur, there is still a large mass from the clutch. Removing it IS a good idea if one wants to free up horsepower- but in truth it's not going to make much difference.

The reason why most vehicles these days have electric fans has nothing to do with them being better. It has much more to do with packaging (it's easier to fit an electric onto the radiator than try to package a large fan attached to the engine- also, most vehicles these days are FWD, which complicates mechanical fan setups to the nth degree. Again, packaging. )

I will agree that electrics help engine warmup. Kinda hard to argue that one, sitting in still air with air being sucked through versus not... especially as we have established that mechanical fans DO constantly move air, even at warmup. No fan clutch ever completely releases the fan.

I think your math for efficiency is a bit oversimplified, too many assumptions.

Above all, you need a very large dose of humility. You come in here and ask a question, and then get testy when people try to help. If you don't want to benefit from people's collective wisdom, try not acting like a 15 year old. Save that for POR.

 

[burntkat]

In the 14 years I have been on , many have here in the hot south-west have tried electric fans...and have gone back to the stock mechanical fan.
No electric fan, that fits, can pull the amount of air that the stock mechanical fan does.

Like David, my XJs run coolest with the stock fans, Mopar HD radiators, along with large coolers for the steering and transmission.

Do you have a PN for the OEM HD rad? I'm looking at possible future upgrade for my new 97, I'm on the fence going for an aftermarket AL/AL or copper/brass job.

 

[JohnX]

Some guys want to reinvent the wheel??

Bricker/Lazy are right, jeep built it right to begin with. Stock setup works the best.

As for a few of you Internet experts.... quit posting bs info. Electric fans do not work well on an xj.

 

[Green XJ Jeep]

Do you have a PN for the OEM HD rad? I'm looking at possible future upgrade for my new 97, I'm on the fence going for an aftermarket AL/AL or copper/brass job.

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