Electric Fan Replacement Recommendation for the Clutch Fan In DMax

**TFEnt** · 08-03-2003, 19:40

Has anyone come out with an electric fan replacement setup for the Duramax yet??

I towed my new 03 out to Tulsa from San Diego a couple of weeks ago through the mountains and the heat and the dang clutch fan never shut off. I figure it killed at least 3-4 mpg from my average during the 3000 mile turn around.

I want to get rid of the clutch fan for good!!

David Utz · 08-04-2003, 05:59

I think you will need to put on an exhaust brake if you do get rid of the fan clutch. I think that most of the retarding force in grade braking comes from turning that fan at high speed.

**a64pilot** · 08-04-2003, 06:28

SSmokeybear,
There are no free lunches, The electrical power required would pull slightly more power than a mechanical fan if the amount of air moved is the same. You see the electric fan would pull slightly more power from the engine as it takes mechanical energy to make electricty to be converted back to mechanical energy and it would be more efficient to use mechanical energy directly.
Electrical fans are more efficient only in vehicles where the fan rarely runs, like in most passenger vehicles at highway speeds.
FWIW I believe electric fans really came into widespread use in front wheel drive vehicles due to the difficulty a mechanical fan poses there.
In short, while it may be possible to replace the fan with a more efficient blade design and gain a little there. I believe that by going to an electric fan you would actually lose more mileage than by staying mechanical.

**Husker Fan** · 08-04-2003, 08:06

It was my understanding that the fan design on the Duramax was really outstanding. I remember reading somewhere that the blades of the fan use technology developed for the US Navy's submarine's fleet.

mtomac · 08-04-2003, 09:22

I hope navy subs are quieter than the Dmax cooling fan

**Amianthus** · 08-07-2003, 08:04

Don't do it. There isn't an electric fan made that will fit and will draw as much air as the stock unit. Performance will suffer. But it's your truck.
The best of both worlds is an electric clutch fan, but I don't think that one is made for the Dmax. They work pretty slick.

Kennedy · 08-07-2003, 11:39

If need be, I could likely dig up the power draw specs for our setup. It is likely 50 lb/ft max...

If the clutch is engaging, the AC, intercooler, trans, and radiator need cooling plain and simple. I guess GM coulda made this one work like the 6.5 and ran overtemp all the time

**Colorado Kid** · 08-07-2003, 13:05

Originally posted by Husker Fan:
It was my understanding that the fan design on the Duramax was really outstanding. I remember reading somewhere that the blades of the fan use technology developed for the US Navy's submarine's fleet.

Actually it's the gassers that got the "submarine" fan , and their fans are much quiter than ours.

I've never felt like the fan on my truck was on when I wouldn't have wanted it on. It doesn't come on unless I'm 1) In stop and go traffic with the A/C cranked or 2) Towing with the A/C on.

Like Kennedy said. I don't have the problem of the fan running when I was towing 70 MPH across the desert with the '88 with TBI 350, because it wouldn't go 70 MPH while towing except down hill, and you couldn't tow with the A/C on unless the outside temperature was low enough that you didn't want the A/C on, cause it would overheat.

It is a pleasure to listen to the fan shrieking right along while running at the speed limit on cruise control rather than podking along with one eye on the temp guage and the other scanning for a spot to pull off the road. I'm not tempted in the least to "fix" anything about the cooling system on the D-max.

If you want fuel economy then slow down. If you go as slow as the 6.5s you'll burn less fuel than they do, and your fan wont engage as often either.

It's mighty hard to go that slow when you don't have to though.

**TFEnt** · 08-07-2003, 19:18

My point to this conversation is this. At 70-80 mph there should be more than enough airflow going through the radiator, coolers, and condenser that a huge clutch fan would not be needed. I feel like it is more of an issue on the Chevrolets because of the huge bowtie on the grill. The GMC truck grill is replaceable with a cleaner billet grill and the aftermarket Chevy one leave the bowtie in place. The Chevy Bowtie is blocking air from entering the radiator area, thus causing the increase in temperatures and causing the fan to continuously run.

At minimum the Duramax should have a duel fan system. Electric fans on the front of the condenser/radiator and electrically activated clutch fan for low speed large air movement needs. At freeway speeds if additional air is needed for the A/C then and electrical fan should kick on and cover those needs. The Tranny cooler should also have its own fan on it like the better aftermarket ones do.

I want someone top make a new billet grill with the bowtie removed. Then test that configuration. I will be adding an electronic fan to the condenser for low speed A/C needs. The tranny cooler will also be upgraded to an electrical set up. After this I believe that even at high speeds in high temperatures that a secondary electrical fan can dramatically improve fuel mileage.

Kennedy · 08-07-2003, 20:43

You can only ram so much air through the radiator before it needs help. Aerodynamics, static pressures etc play into this.

Ever measure compressor out temp? You'd be surprised. EASILY across 400

**dmaxalliTech** · 08-07-2003, 20:50

If you added fans to all those coolers, you could take off the bumper, you wont need it anymore. You would have to get hit by a cement truck to get to the fan!..

**TFEnt** · 08-07-2003, 20:51

Kennedy:

Can you explain to me why on a 65-70 degree day starting a cold motor with the a/c on and the clutch fan is on when you leave the driveway? We are talking less than 10 seconds after starting the motor and you move. This can not be from the condenser. Something else is making the clutch fan turn on.

I believe the current clutch fan set up is inefficient.

Keep in mind I am not being confrontational just trying to figure this thing out with the help of other knowledgeable forum members.

**gardnerteam** · 08-07-2003, 21:21

I KNOW I'm gonna get buckets of ---- thrown on me for this response, but since no one has said it, I'll take the heat. The GM fan on the D/A may be considered fuel inefficient, but it is sure efficient at keeping the motor, air conditioning, and tranny COOL, which is what it's purpose it. I have towed up to 33,000 lbs with 103 outside head over the notorious Grapevine in California with engine temps about 205, and tranny temps the same, all with my air conditioning at full blast. I know of no electric fan that will move the mass of air the D/Max fan does. We all remember the 6.5 fan which did not do a cooling job and for me caused engine temps of 270 with tranny temps spiking at almost 300. Kennedy now sells a fan to cure this problem I understand and it is not an electric fan. Electric fans have their place, on light cars, street/strip cars, and even on my 57 383 FI stroker, but not on a heavy diesel truck used to tow. You need to flow air volume under heavy loads which most electric fans do not do. Go ahead - throw it now.

**gardnerteam** · 08-07-2003, 21:24

I KNOW I'm gonna get buckets of ---- thrown on me for this response, but since no one has said it, I'll take the heat. The GM fan on the D/A may be considered fuel inefficient, but it is sure efficient at keeping the motor, air conditioning, and tranny COOL, which is what it's purpose it. I have towed up to 33,000 lbs with 103 outside head over the notorious Grapevine in California with engine temps about 205, and tranny temps the same, all with my air conditioning at full blast. I know of no electric fan that will move the mass of air the D/Max fan does. We all remember the 6.5 fan which did not do a cooling job and for me caused engine temps of 270 with tranny temps spiking at almost 300. Kennedy now sells a fan to cure this problem I understand and it is not an electric fan. Electric fans have their place, on light cars, street/strip cars, and even on my 57 383 FI stroker, but not on a heavy diesel truck used to tow. You need to flow air volume under heavy loads which most electric fans do not do. Go ahead - throw it now.

**CONCORDMAX** · 08-07-2003, 22:03

SSmokeybear,
I just got back from a trip to Colorado, Lots of mountians and heat. The only thing I hated about the trip was we took it in a Powerst**ke. You think the Dmax fan is loud and bothersome. After about an hour of listening to the pulseating and loud sound out of the pst**ke I was about ready to shoot myself. I know it might not mean alot but the fan in the Dmax works well.

**a64pilot** · 08-08-2003, 07:09

SSmokey,
The easiest thing to do would be to run it without a grill at all, I don't think you'd notice much difference.
I'm not John, but the answer to why the fan runs at first start up is that the fluid in the clutch is thick when cool and causes some drag. All viscous clutch fans do this, not just the Dmax's.
BTW, the reason that the bowtie wouldn't block much airflow is that it is at the center of rotation of the fan blades, even if the blades went all of the way to the hub there is very little rotational velocity towards the center and therefore not much airflow.
I believe your pretty much stuck with the fan as is, IMHO there is not much room for improvement.
It's probably the intercooler that causes the fan to run so much when the truck is under load. Fifth stge bleed air in a turbine is about 400deg., the shaft driven compressor on an Apache helicopter's discharge temp is about 400deg. I'll bet the turbo discharge temp above say 20 lbs. of boost is up around 400deg. or so. If it is then that's a boat load of heat to get rid of. Boat load = big fan

**TFEnt** · 08-08-2003, 08:28

Ok, I now understand the clutch hooking up at start up. But here is my argument about the bowtie.

At speeds above 40mph:

There should be sufficient airflow across the radiator, air cooler, tranny cooler, and condenser not to have the clutch fan running.

The bowtie and chrome plastic strip is preventing airflow to enter the radiator area at all both above and below it. Or it is serious decreasing the amount of air entering that area. Because of the size and angle of the bowtie and plastic strip I believe air is being deflected over the hood because it protrudes out farther than the grill area. Thus causing increased temperatures in the cooler area and causing the clutch fan to run while at high speeds. Where are the aerodynamic specialists on the forum???

**DalDMax** · 08-08-2003, 08:38

SSmokybear,
Are you hearing the fan while the engine is cold past the first 3 or 4 minutes? I'm not hearing the fan on mine in the mornings unless I've really been on the go stick.
Maybe you have a over active fan clutch?

On the way in to work this week the mirror has been showing anywhere from 83 to 86 degrees at 7:00 am and after the first couple of minutes I don't really hear the cooling fan.

Now on the way home that's a whole nother story

**Colorado Kid** · 08-08-2003, 10:17

I have a hunch that the California Emmissions sticker is related to how often the fan runs. Do the CA trucks have EGR? If they do that can explain a "boatload" of heat all by itself. Even just the Catalytic Converter proably contribtes some heat in the form of backpressure.

**J Dawson** · 08-09-2003, 17:10

I've read that a radiator only needs an opening for air 1/4 of the area of the radiator. If you think about it it makes sense. The fins and tubes that make up a radiator take up a lot of space. Adding up the 4 coolers that most of us have on our trucks and the Bowtie probably doesn't matter.

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