ScottyBoston

Hey Guys,

I noticed the other day that my fan is completely engaged at cold start-up, which was concerning to me because the temperature hasn't risen above freezing for about a week up here. It’s not just that the fan is spinning, either. It’s definitely howling, and in direct proportion to the RPMs.

It’s probably worth noting that I recently replaced my exhaust from the cat back, the result of which was a significant reduction in noise. So, I’m wondering if I’m just now noticing an actual problem, or I’m just getting used to normal operating noise versus that with a crappy muffler. Btw, I have a 2004 5.4 with 93K.

I tried researching the topic on here, but can’t find anything to help me determine:
1. Is this normal?
2. Tips for further diagnosis

Any help would be greatly appreciated!
For reference, below are a couple related threads that discuss this, but don’t really answer either of the above questions:
Discussion on the benefits of an electric fan versus thermal fan clutch:

https://www.f150forum.com/f4/removing-clutch-fan-49902/

Thread that discusses aftermarket fan and the issue of engagement at cold startup (that is, after replacement):

https://www.f150forum.com/f4/04-5-4l...issues-160403/

-Scotty

gerald07

Has the fan clutch been replaced at all?

ScottyBoston

I'm not sure - I've only owned the truck for about 6 months and I have very little (if any, really) service history on it.

rmp213

to diagnose a fan clutch, what you want to do is have someone get in the truck while its idling, have them cut the wheels to full lock in either direction, if you hear it start to make a clicking noise at full lock, its time to replace it. It's a fairly inexpensive and easy fix, just make sure you don't over torque the bolts when you re-attach the fan blades to the new clutch. It's cast aluminum and you'll mess it up if you over-torque

alsatropine

iTrader: (2)

If you're gettin a whining noise like a jet engine and its consistant with the RPMs then more than likely its the bearings in the alternator. Im having mine replaced Friday. Sounds like I have a supercharger. It just started when the first real freeze came in. I live in North Alabama so this year it hasnt gotten that cold. Its 70 today. It'll be 43 tomorrow. Go figure. But anyways, it was a heck of alot cheaper to replace the bearings than to replace the whole alternator. 45 bucks compared to 200+..

ScottyBoston

It's definitely not a whine, but more like a whooshing sound, like a hurricane. I'm going to see if it does it with a warm (not hot) engine too so that I can rule out the possibility of it just being partially engaged when cold (after further review, it seems that many folks find this to be normal operation).

gerald07

Well my guess us that it has been replaced. The sound you're talking about makes your F150 sound like an 18-wheeler I'm guessing? If it was replaced, then that is your answer. Aftermarket parts apparently cause that. And I'm willing to bet it goes away after about 10-15 minutes of driving?

B-xp

The fan will be fully engaged at cold start as the silicon fluid is very viscous when cold. It will slowly disengage as it warms, and once it warms to operating temp and the required temp to allow the fan to lock it will lock. Its normal to have it sound very loud when cold, if it stays on through op. temps there is a problem. If you overheat and the fan isnt cooling properly there is an issue.