Dual electric fans?

[bigmikestud]

In my haste to add, well, add-ons, I decided to get the #280 Flex-a-lite fans for my'96 6.5. It runs hot, hotter than my '97 did and I've always like the concept. I haven't ordered them since I've never seen anyone brag about them on here or elsewhere. Tell me, why not use them? They are expensive as he$$.

[CleviteKid]

The engine-driven fan is NOT the bottle-neck in cooling, if the fan clutch is still functioning properly. The cooling modifications for the '96 era trucks as promoted by TheDieselPage.com will solve overheating problems when properly applied.

The add-on fans you are looking at just cannot move the volume of air needed to cool an engine and radiator choked by one inadequate thermostat, and with a less-than-monstrous water pump. If you post a question on the 6.5LTD Forum asking for advice on how to cool your '96 truck, you will get plenty of very good advice.

Those advisors are also welcome to add to this thread in "Ask Dr. Lee" for your and our convenience. Less traffic here, so it will be easier to find the answers.

Dr. Lee :cool:

[gmctd]

To address the initial heating problem, check the areas between the oil cooler and the ac condenser and the radiator for leaves and junk.
Cleaning there will help.

Late '96 trucks got the '97 dual thermostat housing and a hi-flow water pump, with HD casting mark.
Check the picture in my signature for a good shot of the dual T-stat setup to determine if your truck has this upgrade.
If so, the original t-stats may be defective.

A similar, single t-stat housing was available for the non-turbo trucks - the single cover is flatter on the passenger-side.
There is a picture of the single t-stat housing on John Kennedy's website.

Final step is a custom calibrated fan clutch from one of the DP advertisers - engages at lower-than-factory setting, for excellent cooling.

A factory 21" hi-output fan is also available.

Some furthier info on cooling is available in the Members' Area, iirc.

[ 04-23-2004, 07:32 AM: Message edited by: gmctd ]

[More Power]

Here's an email exchange I had with a member yesterday that discusses cooling....

At 09:01 PM 4/21/04 -0500, you wrote:
>I have been reading the section about overheating in the troubleshooting
>guide of your web page. My truck is a 1996, 3500. 6.5td dually. In
>your overheating guide there was no temp indicated that would be too
>hot. My temp gauge shows redline at 260 degrees. It can run 210-240
>degrees at times while towing. What is too hot in my 6.5td?? Also is
>it possible to tell what capacity my water pump is, or where they all
>the same for the 96 6.5?? Stock should be 86gpm with an aftermarket of
>130gmp at Kennedy's. As far as the fan clutch, the troubleshooting
>guide said that the factory clutch should engage at 150 to 165 degrees.
>The Kennedy web page said that it would not engage until 195 degrees.
>What is the difference there? Also had my radiator flushed and they put
>in the green to replace the pink. That did not sound right either, what
>is your opinion on that??
>
>The article is very good and down to earth, enjoyed reading it. Just
>want to get my truck to max cooling for towing.
>
>Rusty

Hi Rusty,

What's too hot is subjective. I consider anything over 220 as too hot, but your engine computer will begin pulling fuel (reducing power) at approximately 235 degrees. I much prefer doing what's necessary to control temperatures so the engine never exceeds 220 - no matter what.

GM specs for fan-clutch engagement varied through the years. The 6.2L diesels were at 165, the first few model years of 6.5's were at 195, and the newest 6.5's were at 205...

I prefer to have the fan clutch engage before the engine reaches 210 - preferably around 205. You will not be able to keep the 6.5 cool unless the fan-clutch engages properly.

Robertshaw 180 degree t-stats will cause a factory calibrated fan-clutch to engage about 5-10 degrees cooler because hot coolant begins circulating through the radiator sooner - hence sending hotter air to the thermostatic coil on the fan-clutch sooner.

If your engine's thermostat housing contains two thermostats, you have the 130-gpm water pump and hi-cap cooling system. If your engine has just one t-stat, you have the 87-gpm cooling system.

Here's what I recommend - get a lower calibrated fan-clutch from Kennedy Diesel, buy a Duramax 9-blade 21" fan, and install Robertshaw 180 degree t-stats (and the hi-cap cooling mods if yours doesn't already have it).

The previous paragraph will solve 90-95% of all cooling problems. For those that are still getting too hot, you are working the engine hard enough to require an intercooler and free-flowing exhaust system. The Spearco intercooler from Kennedy is the best bolt-on kit currently available. The Turbo Technology intercooler is good, but not as good as the Spearco.

Going custom, such as modifying a Dodge Cummins intercooler will be as or more expensive than the Speaco 6.5 intercooler. peninsulardiesel.com is supposed to be working on a new full-width behind-the-grille intercooler for the 6.5 trucks/Suburbans, but I haven't heard a schedule for introduction.

If your engine came with Dex-Cool coolant (the pink/orange stuff), that's what should have been re-installed. Dex offers a higher coefficient of heat transfer and longer water pump life.

Good luck,

Jim Bigley

PS. Regarding whether dual-electric cooling fans will help..... The highest rated dual-electrics pull 5200 cfm. A Duramax 21" 9-blade fan will pull more than 10,000 cfm at 3000 engine rpm - or about the same as the dual-electrics at 1500 rpm. Electric fans take power to turn, and I'd recommend an alternator upgrade if you go that route.

[ 04-23-2004, 09:28 AM: Message edited by: More Power ]

[tom.mcinerney]

Earl's Performance makes a business of aftermarket/racing automotive plumbing products. I read their advice before installing an oil cooler on a car a couple years ago. They advised never install fans on both sides of the heat-exchangers. I guess if the fans aren't perfectly synchronised they 'fight' each other...

[Bobbie Martin]

Some GM trucks came with auxiliary electric fans in front of the radiator. A friend of mine has a 2500 7.4L (454) Suburban with one. Another friend has a much modified Mini Cooper S (the old "real" one) he drives every day and it gets pretty hot down here in Florida. They are known to overheat at the drop of a hat. In addition to a special oversized radiator he has an electric fan on the exhaust side of the radiator with the engine driven fan on the inside (Mini radiators sit on the LH side of the engine compartment and the engine driven fan blows through the radiator). Anyway, the point is it will overheat on a hot day without the electric fan on. So I'm not so sure having a fan on both sides is a bad idea. Seems to work for him and GM.

[ 04-23-2004, 07:21 PM: Message edited by: Bobbie Martin ]

[bigmikestud]

I'm wondering if the FSD/Cooler from "The Diesel Doctor" could fix this problem?

[whatnot]

Originally posted by bigmikestud:
I'm wondering if the FSD/Cooler from "The Diesel Doctor" could fix this problem? I hope that was a joke. :eek:

[tom.mcinerney]

Bobbie Martin-
I just reviewed my "Earl's Performance Plumbing" catalog. NO mention of fans, at all. I guess i've got (another) memory/attribution problem. THANKS for helping out.
I do think i've read that unmatched fans can be counterproductive. I also know that counterrotating props work on boats and aircraft.
I think the tradeoff may involve conditions, as racing/highway vs idle/traffic. The near-universal use of electric fans on modern autos shows that the engine-driven fan does nothing to alleviate heatsoak following shutdown. The radiators/oil coolers are near useless without airflow; at low speeds any increment in flow probably helps. At high-speed/load conditions I'd think multiple fans would need to be matched .

[Craig M]

Just remembered one nice reason for the electric fans. Having a 100 plus degree hot spell this week. Pulling a heavy load in stop and go freeway traffic. You get littel fan speed from the engine fan with the engine idleing, and no vehicle velocity to push air through the radiator. You can just watch the temperature gauge go up. I have personally had more problems with this on gas vehicles, but some of the same applies to diesels

[britannic]

A big plus with diesels is that idling doesn't shutdown the air flow into the cylinders to just a trickle like a gasser. Plus only enough fuel is injected to maintain the idle speed, so they don't generate as much heat as an idling gasser.

In fact, Cummins recommends not idling too long in colder weather as the cylinders get cold enough to condense the injected diesel and heavy carbon deposits start forming along with fuel diluted engine oil.

[ 04-29-2004, 08:46 PM: Message edited by: britannic ]

[NH2112]

Originally posted by Craig M:
Just remembered one nice reason for the electric fans. Having a 100 plus degree hot spell this week. Pulling a heavy load in stop and go freeway traffic. You get littel fan speed from the engine fan with the engine idleing, and no vehicle velocity to push air through the radiator. You can just watch the temperature gauge go up. I have personally had more problems with this on gas vehicles, but some of the same applies to diesels If the fan clutch is working, and the rest of the cooling system is up to par, this shouldn't be a problem because the fan will spin at engine speed. Even at a 650rpm idle a locked-up fan clutch will move a LOT of air if you have the 6-blade 6.2L fan.

[More Power]

Most new cars are using electric fans because of the transverse mounted engines they use. There's no easy way to get an engine driven fan in those situations.

Electrics can work in some situations. I plan to use an electric(s) in the Duramax Project truck for two reasons: 1- Allow the engine to reach near op temp faster (while at the track). 2- Want the hp to go to the wheels.

For those who tow, an engine driven fan is the best choice. Better cooling ability. If you don't tow, or spend a lot of time in suburban/city traffic, an electric fan set could have an advantage. However, you should consider upgrading the alternator if you go that route. The bigger fan-pairs can draw 30-50 amps. The factory original 105-amp alternator isn't capable of delivering 105 when hot.

MP

[CleviteKid]

MP: The same full-throttle micro-switch that turns on the nitrous is gonna turn off the electric fans ?

The Clevite Kid :D

[Len Whitney]

I have been runing the Flex-o-lite fans for over 2 years now with no problem have not towed anything yet and I only have the single thermostat, but made a run to Mesa Az last year from the Pacific Northwest AC and all.
Sure took alot of weight off the front of the engine.

[NH2112]

Originally posted by More Power:
I plan to use an electric(s) in the Duramax Project truck for two reasons: 1- Allow the engine to reach near op temp faster (while at the track). 2- Want the hp to go to the wheels.Everything I've been taught and told says that a load is a load, regardless of whether it's x HP being sucked up by the mass and inertia of an engine-driven fan or x HP being sucked up by a harder-working engine-driven alternator supplying extra current to run electric fans. TANSTAAFL!

[CleviteKid]

Phil:

The electric fans can be on a switched circuit, so MP can turn them off for the seven or eight seconds it will take him to reach the 1/4 mile lights.

The Clevite Kid ;)

[moondoggie]

Good Day!

Seven or eight seconds, huh? I think he'll be going so fast he'll have to put a shutter in front of these electric fans, otherwise they'll be spinning so fast from the air coming in the front of the truck that they'll generate massive amounts of electricity, which will probably cause the battery to explode. Man, I want to be there to see THAT pass!!!!! :D

Blessings!

Brian Johnson, #5044