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engine fan issue

1K views 3 replies 2 participants last post by  DMc 
#1 ·
Hello all, my truck is a 2005 f550 tow truck. 6.0 auto. No mods. A couple days ago I noticed that my fan was running hard for an extended period of time. Fan was louder and gets louder with rpm increase. I didn't think anything of it as the truck had been running all day. The following morning after it cooled off, I started the truck and drove off shortly after before the truck had the chance to warm up and could still hear the fan blowing full force with rpm and it hasn't stopped since. I checked the coolant level, no change. I've monitor my temps on the scan Guage and have noticed a decrease in eot, wt, and trans temp. It's running on avg. 10 degrees cooler than usual. I've done some research and suspect it's my fan clutch but would like to verify before spending the money. Could it be the sensor instead? I unplugged it and no change. When the truck is off I can manually turn the fan. I can feel resistance but it does turn. What else can affect the fan speed? Anything else I should check? Any info is greatly appreciated. Thanks in advance!
 
#2 ·
Some of the threads I've read say the fan uses all sorts of info to determine when to come on. You can try unplugging it and see what happens. The connector is right at the top of the plastic shroud. That might point you in the right direction. My fan clutch has gone south a couple of times but it's the opposite of yours in that it stops coming on at all.
 
#3 ·
Thanks for the input! I did unplug the sensor and no change. The fan was still blowing strong. I noticed some greasy, oil like residue around the fan propellers. Could that be the coming from inside the clutch and would it be a sign that it's gone? Or maybe something splashed up while driving.
 
#4 ·
What sensor did you unplug? I was suggesting unplugging the fan clutch itself. If you unplugged the fan and it's still running full blast then I'd say the clutch is locked up. Whenever I've had mine apart I see that same residue around the clutch. Always figured it was some of the viscous fluid that leaked out over time.
 
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