I have a 2021 350 Super Duty/Diesel/10 speed. I live in Phoenix and it is hot. The engine fan on this new truck is engaged way more than any of the other three F350 deisels I have previously owned. It is very loud and sounds like it's ready to blow up. All temp sensors are normal and fuel economy is still good. The fan engages when it is hot and when it is cool, in the morning, and when going down freeway with no load, and city driving and first thing out of the garage. We pulled the 5th wheel to Tucson the other day and the fan was on for basically the entire trip. Is this normal? Dealer says yes. This is really obnoxious- needs fixing. Anyone shed light on this?

 

Fan is engaged anytime the a/c is working.
The percentage of engagement will change depending on what the ecm is sensing from the various temp sensors but will be engaged at all times.

 

Pretty much normal. If the A/C is working hard, the fan will be working hard.

 

Guys-there is something not right here. I drove to New Mexico last week, not trailer no load, empty truck. Temperatures were between 90 and 103 degrees. 650 miles interstate highway driving at 70+ mph. The engine cooling fan was engaged for 95% of the entire trip!!
Feel fan vibration vibration in steering wheel, pedals and seat. Sounds like a semi truck. All temps normal, got 18.7 mpg.

Called dealer two days ago, no call back.
There has to be a fix for this.

 

Coolant temp is what the diesel fans go off of and in stages, the fan clutch is temp controlled. I imagine it's related to a bad temp sensor/ signal/ connection or the electronic clutch module is bad and is engaging.
I think....

 

the fan is near or at full engage at the wrong time. hard to say if its the fan itself or something else sending a bad signal. just tell the dealer its engaging at the wrong time

 

Thank you guys-I'll schedule a visit with dealer and report back

 

90-103* ambient temperature air conditioner was probably cranking, id say it’s normal. It’s an engine-driven fan. Most people are used to the electric cooling fans in their grocery getters nowadays.

 

Doubt anything has changed much with fan engagement programming but my 2018 does not sound like a big rig until my trans temp hits 220ish. Once the temps come down, it loosens up. I hit 235 a few times on trans temp and it got really loud for a few minutes. I agree with you that something is not right; it should not sound like a big rig all the time.

 

If the service manual hasn't changed then it's difficult to diagnose when a fan is on more than it should be. I have a 6.2 2017 and had the same issue. Multiple trips to the dealer with no fault found. I replaced it myself.

The challenge is the service manual does not have anything to determine is the fan is more engaged than is should be or running when it does not need to be. The testing only checks that fan is spinning at least a minimum RPM, there are to max limits (but the manual warms to stay clear of the fan incase it flies apart). Also it does not seem like there are any ECM/PCM checks to see if the fan is spinning more than needed. I can understand this because as you drive at highway speeds the fan will turn from the air just going through the radiator.

One check I think you could do is when the truck is warmed up and the fan is more engaged than it should be, stop turn off the engine and unplug the wires going to the fan. See if the fan is still on. It should only be on a little bit and not do anything when the engine is rev'ed. If the fan is still on and more engaged it's bad. This was my way of confirming mine was bad. I know the fan clutches are not the same between the gas and diesels but they work the same with an electronically controlled viscous clutch. what is happening is the valve in the fan clutch is not closing and the viscous fluid is being let out the reservoir within the fan clutch to between the case and the rotor resulting in the fan being engaged,

Here is an explanation on how they work https://www.gmb.jp/en/product/cooling/fan_clutch.html In our trucks the valve is controlled electronically by a solenoid that is pulsed on and off to get the fan to spin a minimum speed.

And here's a picture of the inside of my failed fan clutch. I did not figure out what was actually wrong with it, gave up before I made to big of a mess.

 

running empty on the highway even in 103f with ac on the fan shouldnt be any where near full engaged. it would lightly engaged but you wouldnt even be able to hear it over wind and tires and radio

 

And it definitely should not be vibrating your seat and steering wheel!

 

1. Turn off A/C see if fan stops.
2. ANY add ons in front of the radiatop? Lights, screen, whatever?

If the A/C condenser is not cooling enough fan will run even at speed.
if there is the possibility of ANYTHING diverting proper air flow through rad the fan will run more.

Good luck getting this sorted out.

 

Ford has replaced my Fan clutch 3 times(2017 6.2L), Not sure if it the same fan in newer trucks but I think it is. my issue was in cold weather startups, truck sounded like a cat stuck in fan.
I would think you have a bad fan clutch as there are a bunch of folks on here that have had them replaced