It freaked me out the first thirty times it happened too. Never had it happen on my 6.0 liter but that was because it was a manual transmission I have to believe. Its normal.

 

Has this been tested at -10F to be of benefit? Or tested like the air intake system in a snow storm? I fully understand the thermostat being closed and needing to work the engine but as an operator of a fleet of school buses in northern Iowa, it would be the absolute last thing we would want. In fact its one reason we pay extra for shutters, winter fronts and on/off electromagnetic or air fan drives.

 

As for where it was tested i do not have access to that information. However, this works different than "shutters, winter fronts etc", with these items you are trying to keep the coolant warm once it has been warmed up and the t-stat opens. With the t-stat closed, the increased air flow will have little to no effect on the water temp as it is already at ambient in the radiator anyway. In extremely cold climates with the fan engaging when the t-stat is closed and the ECT & EOT are cold, the increased load on the engine will heat the engine faster. Once the ECT & EOT rise and the t-stat opens the fan is cycled off not running in the max mode anyway. The fan only cycles to max for a short time when the ECT & EOT are cold and the t-stat is closed. Once the t-stat is open shutters or a winter front are needed to keep the heat in the coolant by limiting air flow through the radiator.

So this is not an either or situation, the two scenarios are complimentary and will work together to allow the engine to warm faster and then stay warm. They are also not just doing this on the 6.4 but has also been added to the 6.0 as well.

 

We do not use shutters and winter fronts to keep the coolant warm after the thermostat opens, we use them to have some hope of the engine even reaching a temperature that the thermostat might open.
Years ago we got rid of the fixed fans, then we ditched the viscous fans as they never fully disengaged, now we run totally on or off fan clutches that we seldom hear engage from November through March.
Ford may have it all figured out in their application but its contrary to anything we have ever found to help in school buses operating in below zero temperatures with 14 gallon cooling/heating systems including 3 or 4 heater cores the size of car radiators.

 

With the T-stat closed how is water flowing from the engine to the radiator and back?

 

It is not flowing to the radiator and back.

 

So how is the radiator having any effect on the coolant getting warm enough to allow the t-stat to open in the first place?

 

It isn't.
I stated;
"We do not use shutters and winter fronts to keep the coolant warm after the thermostat opens, we use them to have some hope of the engine even reaching a temperature that the thermostat might open."

In otherwords we use shutters or winterfronts and totally disengaged cooling fans to cut down on the sub zero temperature air blowing through the engine compartment at speeds up to 100 mph depending on vehicle and wind speed.

 

I follow all of that, and it all comes into play once the t-stat is open.

My confusion stems from the post below,

Since the cold engine strategy, of the fan engaging only when the ECT & EOT are cold and the t-stat is closed, is used to warm the engine faster do to the increased load on the engine, i would think this would be complimentary to installing a winter front or shutters.

 

After reading about this, I thought I would share my thoughts. I have a 08 F-550 and made it's maiden trip to Montana in May. I had the same noisy fan as we are talking about. This is what I sent the dealer when I got back from this trip....

One day in stop and go driving through <st1lace w:st="on">Yellowstone</st1lace>, the fan clutch would come on as normal but instead of going off in about 5-10 seconds, it stayed on. One time for about 15 minutes. The temperature was ok and it was not hot by any means. This was also driving solo without the trailer. I would have thought it would have been a problem with the trailer, not without. Anyway, it did not do it again coming all the way home. We put 4,850 miles on the truck during the trip. I drove it yesterday and no problem. I guess my question would be, should I take it in for service??? It is really noisy when it kicks in and does not kick out. After looking at the manuals, it looks like the fan clutch is also linked to the computer for some information. Used to be just mechanical temperature controlled, now the computer is involved. If you would, run that by your guys and see what they advise….

We have made several trips (Rock Mountains) since then and it has happened several more times. It has never done it with the trailer hooked up, always solo and it has never been even close to hot. Always in the normal range it runs for temperature. The dealer I bought the truck from in Fort Worth said it was in regen but thinks there is a bug in the code that forces the fan to engage even if the temperature is normal. It also seems to happen at higher elevations (8,000 to 11,000 feet). Here in the Houston area, it has not ever done it.... I also think that why the dealer here did not have a clue what I was talking about.....

If there is a fix, I would sure like to have it done. When it engages, it is more than loud and just gets louder the more RPM's you go...... An with the quiet cab in the 08, it just makes it worse....
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Our winter fronts are factory approved and have fixed openings, in no way can they stop all the air entering the engine compartment.
As the ambient temperature drops the number of heater and defroster motors operating inside the bus body increases to the point of possibly never allowing the engine to get to a temperature that the thermostat might open.
I agree the fan being engaged increases the load on the engine. This load on the engine would be the same whether its 100 degrees F or -20 F. I am asserting the warm up value of the fan being engaged decreases as the ambient temperature goes down.
It may be an effective strategy for a high powered diesel engine in a lightly loaded pickup truck. I very much doubt it would be an effective strategy for the diesel engines we have in school buses in the conditions we operate in.

 

Okay now i understand where you are coming from. Not being able to fully close the winter fronts (all the winter fronts i had experience with you could completely close if needed) and having multiple heater cores with fans running will definitely have a major cooling effect. I a agree that the additional load added by the fan being fully engaged is only a minimal improvement and mainly a strategy for the diesel engine in a consumer vehicle that is a DD and operated by people who for the most part do not understand the workings of diesel engines and cold climates. In addition, do to the newer EPA requirements the engines need to be warm for the emissions systems to function properly.

 

I'm having the same loud fan noise only while towing on my 2005 f350 with e the 6.0. It comes and goes as you described.