Electric fan for radiator cooling

[LarryMars]

Here is a photo of the radiator cooling fan combo installed on the back of the radiator to pull air through the core. (Photo was shot from below.)

[sirpurrcival]

So let me play this one back to see if I have it right.

Originally, you had a transmission line going to your radiator, then out, then it when into a secondary cooler unit and the main radiator fan provided the air flow for cooling.

When the belt broke, the mechanic, ditched the radiator part and put two electric fans on the secondary cooler to replace the cooling that you were getting from the main rad fan.

So a couple of thoughts

1. Perhaps the mechanic was wrong when he said the rad cooler didn't really have any cooling effect as he was suggesting that it was more for warming than cooling.
That strikes me a wrong; that would likely get you in trouble on very hot days, i.e. days when you would want your fluid cooled down rather than warmed.

2. Are your fans blowing the right way? The set up that you have pictured suggests electric fans on one side, rad fan on the other side of radiator. If they are working in opposition to each other, I could see that being an issue. Don't laugh, the people who put my supplementary cooler on did just that.

Whatever the explanation turns out to be, if your fluid is getting too hot, your cooling is insufficient or the flow is a problem I would likely rout it the way it was and leave the fans. The extra cooling provided by fans should help keep the system cool. Like another poster suggested, find a way to get a real temperature reading when you are going up a tough incline to make sure.

[pasdad1]

Originally Posted by LarryMars

This dual fan combo is rated at 3200 cfm. It is clear that this is not enough.

Not so fast. These fans are controlled by a thermostat. It is common for electric fan thermostats to be set at a high temperature - say 220 degrees, so that they only run when
absolutely necessary. You might just have to set yours at a lower temperature.

The other thing is where is the thermostat located and what type. The cheap ones attach to the outside of a radiator hose to sense temperature.....as you might expect - this is not accurate. The much better ones screw into the drain cock of the radiator and actually touch the hot coolant. Some are a hybrid, and have a sensor that goes inside the radiator hose, but these are difficult to get a leakproof connection sometimes.

Your thermostat may be a fixed temp design. If that's the case you need a lower temp one, or an adjustable one.

You said you found fans up to 5000 cfm........did you look at the link I posted? Those fans go up to 10,000 cfm !


I would bet money it just the fan thermostat though.


Wire an indicator light in the cockpit that goes on when the fans turn on, so you can visually verify when the fans are on while you are driving.

[LarryMars]

Originally Posted by sirpurrcival

So let me play this one back to see if I have it right.

Originally, you had a transmission line going to your radiator, then out, then it when into a secondary cooler unit and the main radiator fan provided the air flow for cooling.

When the belt broke, the mechanic, ditched the radiator part and put two electric fans on the secondary cooler to replace the cooling that you were getting from the main rad fan.

No. This isn't playing back right. The two fans on the secondary cooler, which the transmission fluid flows through, were there to begin with and they are still there. What the mechanic did was to replace the radiator fan, which was clutch driven, with a pair of electric fans in a shroud that covers the back of the radiator and pulls air through.

So a couple of thoughts

1. Perhaps the mechanic was wrong when he said the rad cooler didn't really have any cooling effect as he was suggesting that it was more for warming than cooling.
That strikes me a wrong; that would likely get you in trouble on very hot days, i.e. days when you would want your fluid cooled down rather than warmed.

This is what I want to know. Is he right or wrong???

2. Are your fans blowing the right way? Yes

[LarryMars]

Originally Posted by pasdad1

Not so fast. These fans are controlled by a thermostat. It is common for electric fan thermostats to be set at a high temperature - say 220 degrees, so that they only run when
absolutely necessary. You might just have to set yours at a lower temperature.

As soon as the temperature gage comes to halfway, the radiator thermostat opens. At about the same time I can hear the fan kick on. It is a 195F thermostat.

The other thing is where is the thermostat located and what type. The cheap ones attach to the outside of a radiator hose to sense temperature.....as you might expect - this is not accurate. The much better ones screw into the drain cock of the radiator and actually touch the hot coolant. Some are a hybrid, and have a sensor that goes inside the radiator hose, but these are difficult to get a leakproof connection sometimes.

Your thermostat may be a fixed temp design. If that's the case you need a lower temp one, or an adjustable one.

You said you found fans up to 5000 cfm........did you look at the link I posted? Those fans go up to 10,000 cfm !

The fan thermostat is in the coolant. The mechanic unscrewed a plug somewhere and screwed in the fan thermostat. Coolant came out during this operation. I thought he said it was in the water pump, but I have not checked this out.

I would bet money it just the fan thermostat though.


Wire an indicator light in the cockpit that goes on when the fans turn on, so you can visually verify when the fans are on while you are driving.

[BFlinn181]

An automatic transmission can create a great deal of heat and requires no warming up by engine coolant. The radiator and transmission COOLER are to shed heat, not warm the transmission. Many folks add a secondary trans. cooler to the regular one built into the radiator, especially if they tow or carry heavy loads, like an RV does. Your RV had an additional trans cooler, whether original or added by a previous owner. Now that the one in the radiator has been bypassed, you only have the separate cooler to keep transmission temps down. I think that besides an accurate temperature gauge with real numbers you should also add a transmission temperature gauge.

The problem with adding a dashboard light when the fan is powered is that it only shows when power is turned on, not that the fans are actually running. I had a 79 Honda with an electric fan. It quit when a mud dabber built a nest in the shroud and blocked the fan. It heated up until the fan hub melted. My first clue was when the car overheated waiting for a red light to change.

[terry735001]

the back plate should not have the long cuts in them that the fan are mounted too

you want to suck the air from the rad so the cuts are not helping

trans cooler should have not been by passed

i hope you have not lost most of the parts to go back to stock

this is the only mod i would have did

Flex-a-Lite Automotive Thread-on Fan Spacer and Adapter

[M&EM]

Originally Posted by BFlinn181

No. If GM took the time to route the transmission fluid through the radiator, I would guess it was to cool the fluid. There is almost surely a grid of pipes and fins to take heat out of the fluid.

The belt driven fan does take horsepower from the engine, I didn't find out how much, in some engines its greater than 10 hp or more. The electric fans do too, just more indirectly because it puts the hp drain on the alternator to create electricity to power the fans. So, you've had the 'drag' of the mechanical fan replaced by the added strain to the alternator (on the same belt?) and it's interior components. Keep an eye on alternator output, you might be stressing the voltage regulator and diodes.

What he says above I agree with

I believe GM's design was to assure cold weather heating of the TF to the temperature of the coolant at the bottom radiator.

This temperature appears to be about 50 degrees cooler then the engine coolant temperature at the top of the radiator. (Typically 195 to 210F).

So given the above, the TF is held to a temperature of about 140 to 155F.

Assumptions are: original cooling system parts in good working condition and reasonable forward movement.

The OE dual fan pack is primarily for condensor cooling assistance for A/C. However, it will also come on at a preset engine engine coolant temperature too, when stopped or in slow traffic.

Since the OP stated he lost fan blade and shrouds, I would guess that shroud and fan had some interference as has been reported many times in the early WHCC model years.

Restoring all the parts and configurations is ABSOLUTELY essential.

[LarryMars]

Originally Posted by terry735001

the back plate should not have the long cuts in them that the fan are mounted too

you want to suck the air from the rad so the cuts are not helping

trans cooler should have not been by passed

i hope you have not lost most of the parts to go back to stock

this is the only mod i would have did

Flex-a-Lite Automotive Thread-on Fan Spacer and Adapter

I was wondering about that back plate, or shroud. The unit was sold that way. I am not sure where it came from, but it was $640.

What is the purpose of the mod that you did? Does this get rid of the fan clutch?

[M&EM]

After having had a fan clutch lock up on my 8.1, trust me when I say you will go nuts with the noise.

For sure the engine will stay cool on hill climbs.

And MPG will drop!

[dieselclacker]

I believe the adapter referenced from Flex Lite is for the proper spacing of the Flex Lite fan from the radiator core. The fan sold by them has flexible blades that allow for varying blade pitch at various engine RPM's. This is not a good idea for your motorhome, in my opinion, because high RPM is required while in a lower gear during assent of long grades in a motorhome. The high RPM results in a near flat pitch of the flexible blades, which moves less air thru the radiator core.This is exactly what you don't want while traversing steep grades.
I agree with M&M, the primary purpose of the stock electric fans mounted on the trans cooler is for moving air across the A/C condenser to make the A/C more efficient at low speeds.

[TAN]

Mine has both the electric fans and the mechanical fan. I am for returning it back to stock.

[pasdad1]

I wouldn't return to using the stock fan. That's 1970's technology. You just don't have a powerful enough electric fan it seems.

Hot rodders use this fan with great success on big block engines. More efficient than the two fan setup in your pictures.


Mount this on the engine side of the radiator to pull air through.

http://www.carcraft.com/techarticles.../photo_02.html

[M&EM]

Originally Posted by pasdad1

I wouldn't return to using the stock fan. That's 1970's technology. You just don't have a powerful enough electric fan it seems.

Hot rodders use this fan with great success on big block engines. More efficient than the two fan setup in your pictures.

Attachment 66285

I don't think the physics involved would show efficiency being better than mechanical clutch driven fan.

Perhaps as a supplement for low speed situations.

Hot rodders don't need to pull 13 tons up 6 % grades for 20 t o 30 miles..