Radiator Fans Wars: Electric vs. Mechanical or Both!

[TemboTusk]

(It's pretty much worthless...
You really used to hit 240* without the mechanical fan?)

Outside temps were 110 to 112 up a long haul from Needles to the Grand Canyon on I40. I would stop, let it idle about ten minutes and would drop down to 180. Again on the climb between Durango and Silverton in Colorado. Temps around 70 to 75 outside.

(BTW, at speed, the fans are not doing anything really anyway.. )

I also figured what could be better than 70 mile per hour wind in the radiator? But, I believe there may be wind deflection around the front of the radiator. The mechanical fan has enough power to overcome the vacuum and suck in the missing air. I have a 1976 GMC motorhome with a 455 engine and when that fan clutch kicks in, you know it. At highway speeds the temp will drop from 190 to 180 in about 20 to 30 seconds. So I think the fans do work at highway speeds.

(How much crap is in front of the radiator?)

The usual; aftermarket bumper, winch and a set of spot lights. Most of it is below the grill or to the side, but there is a bit of restriction.

(Is the radiator Aluminum? If you were replacing the stock radiator with a new one, why would you use the exact same size radiator as the stock one?)

The radiator is brass, but as a triple pass radiator it has a lot more tubing than the stock unit. It is quite a bit heaver also. A good condition stock radiator should do the job. It is just a question how much air is being pulled through the core.

(I like the idea about putting a shroud on your radiator and trying it. But honestly, I believe your radiator does not have enough cooling capacity for your motor.)
I will think positive!

 

[TemboTusk]

I just searched my saved threads and didn't find it, but there is a thread around here on how a guy built a fiberglass shroud. The technique looked fairly simple, reasonably fast, and probably messy like any 'glass project. I believe he did it for his GM diesel swap, so that may help in finding the thread.

I found during my searches:

https://forum.ih8mud.com/60-series-wagons/200130-anyone-have-pics-custom-fan-shroud-v8-conversion.html

 

[Elbert]

PICS1

See first two pics of FJ60 with dual contour fan setup and notice clearance between water pump hub and radiator. Also see two pics that show GM mechanical fan clutch setup on my 01 burban. A little hard to see in the pics, but not much distance between the water pump and the radiator.

 

[Elbert]

PICS2

2nd series of classic pics... 01 suburban for refernece of shroud vs. fan clearance.

 

[Elbert]

I found during my searches:

[URL="https://forum.ih8mud.com/60-series-wagons/200130-anyone-have-pics-custom-fan-shroud-v8-conversion.html"]https://forum.ih8mud.com/60-series-wagons/200130-anyone-have-pics-custom-fan-shroud-v8-conversion.html[/URL]

I like the fiberglass setup....as long as you can keep it away from the fan... though I don't care for flex fans at all. I don't think flex fans move enough air at low speed.

I should mention that I have a B&M engine oil cooler mounted in front on my condensor on the drivers side , don't know how this impacts coolant temps.

 

[ntsqd]

I found during my searches:

https://forum.ih8mud.com/60-series-wagons/200130-anyone-have-pics-custom-fan-shroud-v8-conversion.html

That is the shroud that I recall, but I (erroneously) remembered that there was more discussion about how it was made.

The method that I'm remembering was to use home insulating foam glued together. The first layer was cut to fit the radiator core and the final one or two layers were cut round to the fan opening OD before they were glued in place. The layers in the middle were contoured to blend the two shapes smoothly, painted with latex house paint (anything else eats some foams), and then the lamination process began.

 

[Mace]

(It's pretty much worthless...
You really used to hit 240* without the mechanical fan?)

Outside temps were 110 to 112 up a long haul from Needles to the Grand Canyon on I40. I would stop, let it idle about ten minutes and would drop down to 180. Again on the climb between Durango and Silverton in Colorado. Temps around 70 to 75 outside.

That translates to a radiator not cooling enough when you are actually using the motor. BTW, you have an auto? is it plumbed in the radiator as well? If so, those temps are REALLY bad on a auto...

(BTW, at speed, the fans are not doing anything really anyway.. )

I also figured what could be better than 70 mile per hour wind in the radiator? But, I believe there may be wind deflection around the front of the radiator. The mechanical fan has enough power to overcome the vacuum and suck in the missing air. I have a 1976 GMC motorhome with a 455 engine and when that fan clutch kicks in, you know it. At highway speeds the temp will drop from 190 to 180 in about 20 to 30 seconds. So I think the fans do work at highway speeds.

The electric fans are doing their thing properly if the motor cools off at idle. The motor is not really using the HP, so it takes less to cool it. On those long grades, you are using the HP and the radiator cannot dispel the heat generated by the motor..

(How much crap is in front of the radiator?)

The usual; aftermarket bumper, winch and a set of spot lights. Most of it is below the grill or to the side, but there is a bit of restriction.

I doubt that the restriction is all that bad from the sound of it. At speed it was fine, the problem seems to be when you are using HP (pulling long grades). That is a chronic case of the radiator not cooling enough.

(Is the radiator Aluminum? If you were replacing the stock radiator with a new one, why would you use the exact same size radiator as the stock one?)

The radiator is brass, but as a triple pass radiator it has a lot more tubing than the stock unit. It is quite a bit heaver also. A good condition stock radiator should do the job. It is just a question how much air is being pulled through the core.

Did you bump up the pressure on the system? Double and Triple pass radiators require significantly more pressure to function properly. This may be more of an issue with a stock water pump.. Something to think about at least.

A good stock radiator typically just barely scrapes by cooling a 350, never mind a 383..

(I like the idea about putting a shroud on your radiator and trying it. But honestly, I believe your radiator does not have enough cooling capacity for your motor.)
I will think positive!

Think positive, it may work because the contour fans may be hindering the flow through the radiator at speed. But honestly, I think there is either a hindrance in flow through the radiator, or the radiator just does not have the cooling capacity that you need.

 

[TemboTusk]

I removed the Contour fans this afternoon and installed the stock shroud. I think I will need to build a custom shroud as the stock one is way off.

I will be testing it on a long freeway run tomorrow. It is a route I take often, so I should have a good benchmark. Nothing extreme.

Mace: on the long grades I mentioned; I was running a 4 speed manual trans. I have just installed a 5 speed Toyota trans behind the new motor.

You mentioned the stock water pump may not have enough pressure to fully take advantage of the triple pass radiator. Do you think I should be using a high volume pump?

 

[TemboTusk]

2nd series of classic pics... 01 suburban for refernece of shroud vs. fan clearance.

It is hard to get a straight answer on how far in the blades need to be inside the shroud. Some say, completely outside the shroud, other say a little bit in and other say completely buried in the shroud.

By the look of the stock GM factory shroud and fan; 3/4s in seems to be OK.

 

[Elbert]

your pressure in the cooling system is controlled by the radiator cap...not the water pump, radiator caps come in different ratings regarding pressure. The water pump controls volume or flow. Look at the pics of the suburban which is representative of most any OEM mechanical radiator fan setup you will notice that the radiator fan blades are almost totally within the shroud. The purpose of the shroud is two fold in my mind (1) it directs air flow over a given surface (radiator), (2) it makes the fan more efficient.

Think about it this way.... if you have no shroud and no wind or pressure directing air flow pushing against the radiator what really makes the fan efficient at pulling air across the radiator...nothing really. Given the same event, and you have a ducted or shrouded fan where the shroud captures the body of the radiator on one end and a fan on the other end, you hanve in effect a "tunnel" whereby the fan is pulling air across a defined area (the radiator) and where the fan is made more efficient by only pulling air through the shroud across the radiator, the key is the fan is only pulling air through the radiator.

Look at the toyota pickups with mechanical fans, or the pics I posted of the GM setup, or look at any of the other OEM setups to include big trucks....all have some type of ducted or shrouded fan to make cooling more efficient.

You'll hear different opinions... but always look back to the OEM setups...there must be a reason why they do what they do. My suburban is a 2500 series 4*4 with the 496 / 8.1 engine, to say its a heavy-weight is an understatement... it has the factory 195 themostat, It has a rather large radiator with the nice shroud and fan you see above (All OEM), it never runs more than 205 or maybe 210 on a long grade. The fan clutch cycles with the temps....you can certainly hear it run....but its very effective at cooling the vehicle.

As I recall the OEM yota shroud is off-set of center of the radiator and I thnk your 5.7 sits more on the centerline of the radiator, but any case I would suspect tthat the OEM radiator shroud would not work that well or would hit the fans on a V-8 setup.

I think once you get a good shroud setup you'll notice the A/C works better too, allthough A/C work good with electric fans because the fans generally run at 100% when on.

 

[ntsqd]

The whole point of a ducted fan, as I understand it, is that air can not 'bleed' off the tips of the fan blades. For the fan to work at it's best the air needs to flow over the blades front to back and not slip sideways off the tips. Air that does slip off the tips is lost and effectively makes the blade act like a smaller diameter fan. Ducting a fan puts a "wall" in the way of the air flowing radially off the tips and forces the air to flow front to back across the fan blades.

Putting a shroud tight to the blade tips reduces or eliminates the air slipping sideways off the blade tips. The only reason to make the shroud's opening any bigger than just barely clearing the blade tips is to deal with the engine moving around. As that gap increases the efficiency of the fan decreases.

As far as fore/aft fan placement in the opening, I've heard various Rules of Thumb but I'm wondering at the root of them. Seems to me that ideal placement would have the fan fully inside of the shroud, but one of the RoT's that I have heard/read specifically warns against that.

 

[Dynosoar]

Jim at Downey Off Road has said many times that the fan should be mostly outside of the shroud. After years of extensive lab tests etc. etc. etc. Hey if its staying cool that is good. My 350 will get warm on climbs of longer grades 220-230. I don't see it as a problem the stock thermostat that I pulled out of then engine was a 210 I now run a 190 t-stat. Under pressure and with coolant mixed in the boiling point of the water is much above 230.


Dynosoar

 

[Beerwrench]

I had a similar problem last year with my 6.0 Chevy, I am running the GM mechanical fan with a custom shroud. Turned out my problem was not the fan or shroud but the radiator cap, new heavier cap and now no cooling problems. I was losing coolant through the cap when it would get hot, this only happened at speed so no visual indication was available and the problem only occurred in high temperatures while carrying a load (drive for 2-3 hours then hit traffic, temp spikes on the idle).
My engine temp issues are gone now and I am focused on trans. temp and my AC. AC works but not very good when I am at idle.
I'll have to go look at my radiator, I can't recall the make. it is an aluminum racing radiator, I'll re-post with some more information later.

 

[snowboardonsnow]

I had a 454 (not in my cruiser, I wish) I used the engine fan and mounted electric push on the front of the rad, one auto one manually switched. The truck would never over heat it helped so much.

If you have a good electric fan it will work great, don't buy the bs that it will limit air flow, those suckers will spin up fast at high speeds. And you mount them on the front, and where the engine fan doesnt hit/suck.

Also did this on a 350, in my 85 toyota pickup, only way to go.

 

[lehiguy]

My 350 has never had an overheating issue and I run a stock radiator. I also had to get a higher pressure radiator cap and that helped tons. On the shroud thing, if you look at production stuff, the fan is outside mostly or completely. My 540i (R.I.P.) had the fan outside the shroud, and it was mechanical.

 

[TemboTusk]

I think the fan in or out of the shroud is a fascinating subject. I would love to hear an automotive engineer give their thoughts. I’m sure they test and test and than test some more. Love to hear their reasoning on going one way or the other.

As mentioned in an earlier post; I removed my Contour fans, installed the stock Toyota shroud and gave the wagon an extended 70 mile freeway run.

Temps with the Contour fans alone: about 195 to 200 degrees. The ambient temp was about 92 degrees, speed between 70 and 75 mph. In traffic: temps drop to 180.

Temps with the GM fan alone: about 195 to 200 degrees. The ambient temp was about 92 degrees, speed between 70 and 75 mph. In traffic: temps do not come down unless the engine is at a high rpm.

Temps with the GM fan and the Contour fans together: about 185 to 190 degrees. The ambient temp was about 92 degrees, speed between 70 and 75 mph. In traffic: temps drop below 180.


The stock shroud does not even come close to being adequate. It is as good as not having a shroud at all. I may use my stock shroud as a template for a custom build. After all the discussion, I’m convinced the GM fan with a proper shroud will be a winning combination

I know you will look at the above temps and say what’s the big deal? But, like Dynosoar, it is the long hot grades that creep up the temps. I feel very uncomfortable seeing my gage go over 220 and past 230 degrees. Gas mileage drops, the timing retards and the engine feels anemic. On an Arizona grade between Needles and the Grand Canyon, the temps have gone above 240 degrees. Because of the 16 pound cap, I did not get a boil over, but, I did pull over and let it idle until the temps came down. The rest of that trip was spent with one eye on the road and one eye on the temp gage. It took the fun out of that trip.

Once my new shroud is made and installed, I will post up my temps and hopefully, I will have time to do an extended run up some hot desert grades for the real test!

 

[Elbert]

My 350 has never had an overheating issue and I run a stock radiator. I also had to get a higher pressure radiator cap and that helped tons. On the shroud thing, if you look at production stuff, the fan is outside mostly or completely. My 540i (R.I.P.) had the fan outside the shroud, and it was mechanical.

where are you seeing an OEM setup where the mechanical radiator fan sits mostly oustide of the shroud? I'm of the view that most cars / trucks have the fan blades at least 50% captured or more within the shroud?

I know Downey has his view...but for some reason the OEM mfgs... keep putting fan shrouds on vehicles...

 

[Elbert]

I had a similar problem last year with my 6.0 Chevy, I am running the GM mechanical fan with a custom shroud. Turned out my problem was not the fan or shroud but the radiator cap, new heavier cap and now no cooling problems. I was losing coolant through the cap when it would get hot, this only happened at speed so no visual indication was available and the problem only occurred in high temperatures while carrying a load (drive for 2-3 hours then hit traffic, temp spikes on the idle).
My engine temp issues are gone now and I am focused on trans. temp and my AC. AC works but not very good when I am at idle.
I'll have to go look at my radiator, I can't recall the make. it is an aluminum racing radiator, I'll re-post with some more information later.

Do you have any pictures of your shroud and how you made it? Anyone else have pics or comments on fabbing up a nice shroud on a V-8 engine swap...

Ok..sorry for the highjack...back to normal viewing..

 

[Elbert]

last 2 pics

Ok ..last pics... this time I tried to take pics that were direct line of sight either from left to right or from top / down. Also free shot of the spare tire tool from the 60. Anyway while the fan blade appears to be bent (i first thought that too) the curve and angle is built into the balde, it also has a pretty good pitch to the blade making it take an aggressive "bite" ...

Make your own call...but sure looks to me like the fan is sitting inside the shroud for the most part.

 

[Bret]

For the OEM's another factor may be protecting "people" from getting fingers etc. in the fan blades, my 6.0 fan is almost completely enclosed. Hoping to have roughly half my fan inside the shroud once built.