I have a '06 F250 , 6.0L PSD w/ just under 30K miles.

I've noticed a couple of times now, when towing (8000 pounds or so), when accelerating (not hard, just general accelerating), I get a pretty loud whine for maybe 15 to 30 seconds. Initial reaction was to let off the accelerator. The whine descreased as I did that. When reengaged the accelerator, the whine increased as well. This only lasts for a relatively short duration. I can't say for certain whether engine power was affected or not.. my gut instinct says it was slightly affected; perhaps not as much as I think though, because I let off the accelerator quickly.

I've done some googling and found references to "fan clutch" or "hi temp fan" types of things. I thought I'd get some input from the SD forum here. I'd like to have some degree of confidence for what it is and if I should be taking immediate action. It happened maybe 3 or 4 times in 3 hours yesterday. I have another 3 hour leg to travel today.

Thanks for any thoughts or suggestions.

FOLLOWUP EDIT: After more searching....I think it is very likely this is just normal fan operation ;-)

 

What you're hearing is the "Visconic" fan clutch on the radiator fan locking and unlocking. The PCM controls the fan and locks and unlocks it as needed to maintain engine coolant and trans fluid temps. When it is locked up it is very loud, the higher the coolant and trans fluid temp the faster the fan will spin.

 

A small whine usually comes from the passenger side if the wife is with you. A big whine, that almost scares the heck out of you, is the engine fan.....

 

;-) Thanks for the responses ;-) I'll be ready for the whine(s) now.... now matter how loud.

 

I am pretty sure your fan runs quite a bit while towing 8k or more. The 6.0 fan runs A LOT. Mine probably runs 70-90% of the time when I am towing my 5th wheel camper (8.5K) or my flatbed gooseneck (6k-15K). My water temp also runs right at 220 up to 226 until the fan kicks on and brings it back to 220. Empty my water temp run 200-205 consistently. That little motor builds a lot of heat, something to think about.

 

Wow, your 06 has under 30K miles on it? That is amazingly low!!!!!