Electric fan direction Push or Pull?

[Polo22]

OK, this is a hot topic of late. I ran across and interesting post today in another forum discussing what direction the fans should run. Here is his post:


On a side note: Most people set their temperature control for the fans incorrectly. It should cycle on and off at temp at idle and should shut off if you're traveling more than 35 miles/h on a warm (not hot) day. Why you ask? This saves a ton of wear-and-tear on the electric fan motors and prevents them from overheating. It's not common, but I've heard of fans that have failed because of this. The other mistake is not checking whether you are pulling or pushing air. If you're pushing air, it is less efficient at cooling your engine, especially if you've turned the fan's tempurature control to maximal cooling. You won't notice at a stop light, but as soon as you're moving, the fans are pushing hot air out against the incoming rush of cool air. Your temp gauge will go way up and you'll be wondering why your new e-fans suck ****. It is not as important if you've set the temperature control correctly as mentioned earlier, and the pusher mode may actually reduce your underhood temperatures. Since I have an open element air cleaner, I have set mine up as a pusher. I have also rigged a switch under the hood that reverses the fan's polarity easily (takes two seconds) to switch the fans to puller mode if I need to on a hot day. But so far, I've never had to use it.

Hope this helps.

[John M]

It's really no mystery. If you replace your stock fan with electrics, then they need to pull. If you add an electric fan in front of the radiator to assist the stock fan, it's got to push.

Simple as that.

[89stroker]

:word: i like that answer

[Quyonmob]

It's really no mystery. If you replace your stock fan with electrics, then they need to pull. If you add an electric fan in front of the radiator to assist the stock fan, it's got to push.

Simple as that.

Well put.

[Red94Chev]

This is direct from the Flexalite website: http://www.flex-a-lite.com/auto/html/frequent-question.html

Which type of electric fan is better, a pusher or puller ?
For primary use a puller. For auxiliary use a pusher.

Is there anything I can do to make my model # 150 a pusher ?
Yes, turn the blade over and reverse the polarity of the motor wires. Note: the fan does not run as efficiently in a pusher mode.

When I drive down the road at 55 mph my car over heats, is this a fan problem ?
In most cases no, at 55 mph ram air cools the radiator. Check for obstructions blocking air flow through your grill and radiator.

:smokin:

[SolMan98]

It's really no mystery. If you replace your stock fan with electrics, then they need to pull. If you add an electric fan in front of the radiator to assist the stock fan, it's got to push.

Simple as that.


It's just as simple as that. Mine were set up as pushers out of the box. Just had to flip the blades.

[bizzybone485]

So the best thing to do is replace the clutch fan for electric while pulling air away from the motor into the radiator? Am i understand this right? Thanks

[John M]

You want to pull through the radiator towards the muffler. The whole "blow hot out out through the radiator at low speeds" might work where "hot" is 80 degrees but if you tried it here you'd need at least a head gasket pretty quick.

[bizzybone485]

You want to pull through the radiator towards the muffler. The whole "blow hot out out through the radiator at low speeds" might work where "hot" is 80 degrees but if you tried it here you'd need at least a head gasket pretty quick.

gotcha ...thanks for the clarification

[oldred95]

When your running 65-70 down the road your fans are gonna have to have some nuts to push air back out against the oncoming wind and still move enough air to cool the engine. This dozer we're working on has a push fan but it also has a top speed of like 5 mph so no real oncoming wind there.

[GetMore]

Originally Posted by Red94Chev:
Most people set their temperature control for the fans incorrectly. It should cycle on and off at temp at idle and should shut off if you're traveling more than 35 miles/h on a warm (not hot) day. Why you ask? This saves a ton of wear-and-tear on the electric fan motors and prevents them from overheating. It's not common, but I've heard of fans that have failed because of this.
The other mistake is not checking whether you are pulling or pushing air. If you're pushing air, it is less efficient at cooling your engine, especially if you've turned the fan's temperature control to maximal cooling. You won't notice at a stop light, but as soon as you're moving, the fans are pushing hot air out against the incoming rush of cool air. Your temp gauge will go way up and you'll be wondering why your new e-fans suck. It is not as important if you've set the temperature control correctly as mentioned earlier, and the pusher mode may actually reduce your underhood temperatures. Since I have an open element air cleaner, I have set mine up as a pusher. I have also rigged a switch under the hood that reverses the fan's polarity easily (takes two seconds) to switch the fans to puller mode if I need to on a hot day. But so far, I've never had to use it.

Hope this helps.

This info is going to be confusing because there is not enough info given here. What he is doing is different from what is considered normal for fan mounting. His setup is not necessarily bad, but it has one extra level of complexity that if missing will spell disaster for someone attempting to duplicate this.
Plus, when he talks about pushing and pulling he means airflow against or with the airflow caused by the motion of the vehicle, not the mounting of the fan!

Fans work best when they suck. They are less efficient when they blow.

Normally you want your fan mounted on the engine side of the radiator and running as a puller. This is the most efficient setup, and the simplest. "Puller" in this case means it is pulling air through the radiator.

Red's setup has the fan mounted to blow the air out of the engine compartment, through the radiator, shutting off when vehicle speed increases to the point that the "ram" airflow would overpower the fan. If you were to keep the fan on you would actually stop the airflow, causing the engine to overheat, as he mentions.

The only advantage to his setup is that at idle you are not pulling warm air from the radiator into the engine compartment, therefore the underhood temps stay lower. This sill only be effective at low speeds.

[sack]

Why you ask? This saves a ton of wear-and-tear on the electric fan motors and prevents them from overheating. It's not common, but I've heard of fans that have failed because of this.

The other mistake is not checking whether you are pulling or pushing air. If you're pushing air, it is less efficient at cooling your engine, especially if you've turned the fan's tempurature control to maximal cooling. You won't notice at a stop light, but as soon as you're moving, the fans are pushing hot air out against the incoming rush of cool air.

wear and tear on an electric motor?? uhh sure, it will wear out too quickly and overheat . . . even when it is blowing air accross itself? highly doubtful

as for the second paragraph, this guy is refering to having the fan push air through the radiator from the engine compartment, through the grill and out towards the vehicle infront of him. why would a set up like this make any sense when they origionally pull air into the engine bay??

if you are going to set up a fan to push air, you install the fans infront of the radiator

when installing to pull air you mount them behind the radiator

[sack]

p.s. my previous message was just to chime in and try to clarify the confusing part of the origional post.

after reading it again i noticed that we are basically sayin the same thing and i think that his reversing polarity of the fans could be a pretty good idea.

[SilveradoLQ9]

I have stock e fans on mine, I have always heard that pullers are a little better than pusher fans.

[fernanbfg1]

I saw in a 4 Wheel Adventures magazine, where a guy put a puller fan in the hood of his jeep. Seems to make sense since hot air rises.

I guess it depends on your driving habits whether you need a pusher or puller. If you sit at idle a lot, like in traffic or a construction site a pusher would seem to be better.

[Shawn]

Good god man, it's friggin common sense!! If you dont know/understand how the factory fan is designed to work, you should probably just leave it alone.


If people weren't confused before, they will be now!


fernanbfg1
I guess it depends on your driving habits whether you need a pusher or puller. If you sit at idle a lot, like in traffic or a construction site a pusher would seem to be better.
Assuming you're referring to the fan being mounted behind the rad., then no, it wouldn't seem better. Why would you want to blow hot air from the engine and exhaust manifolds out through the rad??? Certainly isnt conducive to cooling......

[Dubyagee]

When someone can come out with an electric fan that has near the Cfm's as a stock clutch fan without sounding like an air raid siren I'd consider one. But, a puller fan mounted in a radiator matched shroud on the engine side of the radiator is the way i'd go.

[John M]

It's already been said in one of the other E-fan threads but I'll say it again: The fan is only important at a stop and low speeds. Under both of those conditions, the clutch fan isn't being spun much so it isn't flowing a lot of air either. At idle, my electric fans move much more air than the stock fan did.

By the time you get into the upper rpms and the clutch fan starts moving air, the vehicle's moving fast enough to push far more air into the radiator than any fan setup could do. At that point, fan selection is moot.

[Polo22]

It's already been said in one of the other E-fan threads but I'll say it again: The fan is only important at a stop and low speeds. Under both of those conditions, the clutch fan isn't being spun much so it isn't flowing a lot of air either. At idle, my electric fans move much more air than the stock fan did.

By the time you get into the upper rpms and the clutch fan starts moving air, the vehicle's moving fast enough to push far more air into the radiator than any fan setup could do. At that point, fan selection is moot.
Well said Autobot. :rocket:

[Dubyagee]

at idle a clutch fan pulls alot more then (available on the market) electric fans pull wide open. the viscous fluid in a clutch fan is designed to maintain the correct fan speed/efficiency (around 2000 rpm at the fan at any rpm above 2000 engine RPM). If you run e-fans on a v-8 (or any high powered motor) you will see higher heat soak temps and higher full load temps then you would with a clutch fan. Just remember, more cfm = more thermal effeciency.

[sleeper357]

From what i see one of the BIGGEST advantages overlooked in comparing e/fans to c/fans is what happens after you shut down.

My flex-lights continue to cycle after shut down helping to dissipate heat from the block, this is a big issue here in fl and other hot parts of the country.

[Dubyagee]

Your fans are venting heat from an engine that is not circulating coolant. If you had a true cooling fan, It would turn the water pump and the fan. Ive seen drag cars with an electric motor turning the water pump and electric fans. their temp would drop from 200 degrees to 120 in 10 minutes.

[sleeper357]

Your fans are venting heat from an engine that is not circulating coolant. If you had a true cooling fan, It would turn the water pump and the fan. Ive seen drag cars with an electric motor turning the water pump and electric fans. their temp would drop from 200 degrees to 120 in 10 minutes.


Agreed, i was referring to heat soak. In high temp, high humidity areas when you shut your motor off it becomes in effect a pressure cooker the air surrounding the block becomes hotter than the block. Depending on where you live and temp this could be a small deal or a big deal. The e-fans keep air curculating after shutdown a good thing.

[John M]

Well, maybe my fan clutch was dying longer than I thought but my e-fans move some serious air. After all, everyone says you get better AC at idle once you go to e-fans.

Of course I haven't driven the truck in truly hot weather yet (did the conversion a few weeks ago) but so far my engine temp hasn't reached 210. After the 180 stat, the temp actually stays just below halfway on the gauge, or around 150-170 (as accurate as it is, I know). I haven't towed, and probably won't do any serious towing except a car every now & then, so I won't be working it all that hard.

So far I'm very happy with the conversion, and combined with my other mods its enough to make me start to plan replacing the open diff with a limited slip! This old TBI may not make the power the new trucks do but it isn't bad either!

[Eddie Sova]

OK, this is a hot topic of late. I ran across and interesting post today in another forum discussing what direction the fans should run. Here is his post:
Well as of today I installed a Flex-a-lite #280 with a larger raditator...The fans as Pullers...install time was 3 hours..
I had questions about e-fans...and Flex-a-lite answered them all.
I use my 92 K1500 for work towing 2000 lbs ....So far no issues.

[phatchevy06]

at idle a clutch fan pulls alot more then (available on the market) electric fans pull wide open. the viscous fluid in a clutch fan is designed to maintain the correct fan speed/efficiency (around 2000 rpm at the fan at any rpm above 2000 engine RPM). If you run e-fans on a v-8 (or any high powered motor) you will see higher heat soak temps and higher full load temps then you would with a clutch fan. Just remember, more cfm = more thermal effeciency.
:word: Well said.

This is a good thread.

[BillyC]

I tow a 9000# camper once a month with my 03 Sierra HD, I have done the cat back, the intake, a 160 thermostat and a wester's. Would you stay with the clutch fan or go e-fan?

[grey86carryall]

I have in my past broken the spider gears on a subaru, causing a nasty overheat situation when I had to drive in reverse all the way home , the fans fought the backwards airflow. I also note that 4wd subari (old cheap beater ones} have both electric and clutch fans. I am elderly enough that I remember when the automakers switched from direct fans to clutch ones and all the claims of big gas milage improvement.

Most tractor trailers use a temp switch controlled air powered clutch for thier fans, they take about 50 horsepower to turn at speeed so when not climbing a hill they just freewheel. This type of fan usually has an override switch so you can use it to help slow you going downhill, an adaptation of this would be Ideal I think, because the freewheel feature causes less drag at speed. You could also tie it in to your a/c cutout so it did not operate at full throttle. This setup would be the ultimate because no drag or resistance when unneeded, massive capacity (like a direct drive fan ) when needed and less power consumption due to not converting the energy from mechanical to electrical and then back to cool the engine. For all I know this is already made by someone but I would use an electric clutch instead of air.


Stick with the clutch fan for now BillyC

[Crews Customs]

i just ordered some LS1 fans... does anyone know if they are pullers or pushers, or can they be either?

[F-Bobby]

i just ordered some LS1 fans... does anyone know if they are pullers or pushers, or can they be either?

those are pullers.

after reading this thread i think everyone wording the same thign different ways is confusing people.

Typically, if the fan is in front of the radiator (not between the engine and the radiator) its a pusher fan. and typically if its behind the radiator (bewtween the engine and the radiator) then its a puller.

ive never heard of a pusher fan being mounted behind a radiator. That just doesnt make any sense, why would you want to blow hot air from your engine/ manifolds on to the radiator which is trying to vent heat from your already 200+ degree coolant? you want the air to be as cool as possible to help with the heat dissapation.

im gonna be removing my clutch fan and putting in Dual electric fans out of either a 3rd gen F-body or a 4th gen f-body to help keep the engine cool. then i wont have tow worry about the clutch fan breaking and staying engaged all the time.

[GetMore]

I saw something interesting the other day on a Trailblazer. It has a mechanical fan with an electric clutch, kind of like grey86carryall mentions. I think Jeep uses the same idea, as well. I don't know what other manufacturers do.

They fan clutches are not on/off, but are pulsed to control the fan speed. If a retrofit control could be rigged up this would be an awesome upgrade.

[91chevZ71]

mine are pullers, between radiator and engine. works nicely.

[RatPoweredTruck]

fans work best when pulling air even at higher cruising speeds due to the natural flow of the air into the front of the vehicle.

[3day]

I have a question, my buddy has an s10 with a small block 350 in it as a project. He bought a Be-Cool radiator and a flex-a-lite dual e-fan for it. We cant mount the fan on the inside of the radiator near the motor due to his pullies stick out to far and hit the fan housing. I was told I could reverse the polarity and mount the fans on the front of the radiator. Would this be ideal? This wont be a daily driver, but it will get driven on nice days. Is he at risk of over heating constantly?? Any help would be greatly appreciated!