Hey everyone,

Is there any "certain" way to tell if a fan clutch needs replacing? Here is what I'm experiencing . . . and I'm not sure if it is the fan clutch

When it is cold outside, (used to have to be well below freezing . . . now anywhere right around freezing and colder), I am getting a strange chirping or almost a scraping type nose coming from the fan area. The noise definitely does not sound normal. I listened to my buddies trucks (same F-150's) and theirs does not make this noise when they are cold. It is a different noise than the "roaring" that seems to occur when the fan fully engages.

The fan also seems to run all of the time. When I look at the fan with the hood up, it is quite often running even when it is very cold out . . . and for extended periods of time (well over a couple of minutes). It never really seems to "slow down". I did a search of previous posts and from what I understand, the fan will always "freewheel" but only "kick in" when the engine gets hot. It seems like mine has a mind of its own. Sometimes it looks like it's freewheeling and other times it will run full out, even though the engine isn't hot. And then there is the weird noise I described earlier.

Yesterday I noticed that when I shut the truck off, it sounded like the fan continued to run for a few seconds and I could hear the chirping noise as well. Would this indicate a bad fan clutch?

It's on a 97 F-150. Are these a common problem?

Thanks!

 

if i were you and suspected a noisy clutch, i would just take the fan off and start the engine see if its still there. if its gone then you got it. Dont run it till it gets hot though lol

 

That's not how the fan clutch works. The clutch on the fan doesn't care if your engine is cold or hot, it only cares about the RPMs of the engine. Our's are supposed to kick out at about 2K RPMs. It serves many purposes by doing this. If your engine is turning over 2K then the truck is probably going fast enough to allow the natural airflow through the front of the truck to cool the radiator, if under 2K the opposite is true and the clutch engages the fan to pull air through the radiator. To answer your ? with the engine off, spin the fan by hand, if it spins more that a quarter turn, replace the clutch on it, generally a faulty fan clutch will = an overheating problem.

 

Have they switched from thermal clutches on the newer trucks? Thermal clutches are in fact heat dependant.


Another misconception is that the fan will totally free wheel, which it will not. If the clutch is gone, you will notice that fan speed doesn't increase much when you rev the truck quickly. When you first start it up the fan should appear to change speed almost directly in proportion to engine speed.

You should also get the "roar" on cold start. Wait until it settles down, then block the radiator with blankets, rags, whatever. Have someone sit in the truck to monitor and make sure the temp stays safe. As temp of the truck comes up, the "roar" should come back. If it does, remove the rad obstructions, and the truck should cool back down fairly quickly.

If the roar doesn't come back, the clutch is most likely gone.

This would apply only to thermal units.

 

I was under the impression that these fans were both thermal and cytrifugal.

the fan should spin freely when the engine is off.

 

Now I'm confused

Is the fan supposed to spin freely when the engine is off or not? I spun it this morning with the engine cold, and it was tight. It would not move more than 1/4 of a turn . . . if that. When I started the truck, the fan was blowing enough air that it would move my jacket sleeve when my arm was sitting over the battery. It was quite loud although I understand that to be the "roar" on cold starts (and normal in that situation from what I've read).

It did seem to get quieter as I started to drive although the scraping/chirping noise was still apparent. I also played around today and started the truck with the hood up and noticed a scraping sound that lasted for about half a second when the truck first started up. I also hear the noise for a second or two after turning the engine off. Someone else suggested that this may be a bearing in the alternator.

Perhaps I have just been focusing on the wrong part?

Thanks for all of your help, it is appreciated!

 

sorry for the confusion. when I said freely I meant that you COULD spin the fan with the engine off. Not that it would just wiz around when you spun it.

Yes it should spin sort of firmly.

How old is your serpentine belt? Take the belt off and spin each pully with your fingers and see if you feel any roughness or grinding. If you do that usually means that part is bad or going bad.

Is you HVAC set to off when you start the truck? If not the noise could be the Air Conditioner compressor kicking on briefly.

Check your fan shroud for wear. If the bearings are bad in the fan or water pump the fan might be sagging a bit at start up and shut down and rubbing the shroud. (Just a wild guess)

 

I would suspect either a bearing in the idler or the alternator. Sounds to me like your fan clutch is working normal. I don't think there's been much problem with fan clutches. I have heard of some idler and alternator problems.

 

hcmq is correct on the fan moving. It will spin, just not freewheel completly and move very far.

If the fan clutch was squeaking it world probably do it most of the time, since it always turns at least some. The statement about the squeaking continuing after you turn the truck off is confusing though. Does it only continue until the engine stops or after?

I would suspect the belt tensioner myself. My truck got a similar noise after a trip through the car wash one day. Using tubes and spinning accessories I convinced myself the alt was on the way out. Turns out that wasn't it. Same with the air pump. In the case of the alternator the brushes were worn anyone so nothing lost. In the case of the air pump it was real cheap with exhange, and it wasn't worth the $25 to take it back off to return.

I tried a new belt but the squeak didn't go away until I got a tensioner. On my '95 if you are REALLY careful you can add a little bit of tension with the engine running to check.


From what I have seen tensioners that are on the way out tend to start bouncing a little bit more, and I think this creates the squeal.

 

Hey signmaster,

The noise continues for a few seconds after the engine has been turned off and the belt has stopped spinning the pulleys. This is why I think it is fan related. The fan still spins for probably 4-5 revolutions after the engine is off and the sort of "grinds" to a stop. It also makes a harsh noise when the engine first starts and the fan engages.

Because the noise still occurs after the pulleys are not engaged by the belt, I'm pretty sure it is not the alternator or the idler pulley. I'm just not sure if it is the fan clutch or if there are bearings in the fan assembely that may be gone as well.

Does this make sense?

Thanks!

 

I'm not going to add to the confusion however I will bet the clutch is on it's way out from what you described originally. The chirping noise in cold is tell tale. I just went thru this with mine. Before to long the clutch will probably sieze up and roar at any temp, any revs, any speed.
I would pull it off and start it for a short time and listen for the abnormal noise.
Don't buy the Autozone junker for $54 (Imperial) money was tight and I did, I'm on my third one in 3 months. Get the OEM for about $150 or go with an electric fan set-up, that's my next plan.
Good luck

 

Sounds like a good time to add electric fans!!!!

 

Well I've pretty much confirmed that it is in the fan. I was playing with it today and the fan made that same noise when I was turning it by hand and the engine off. This is the first time it has done that so I suspect it is getting ready to go completely kaput.

I've ordered a new fan clutch and will be installing it this weekend. I'll post an update after it's in.

Thanks for all of your help!

p.s. I was considering the electric fan kit but I just don't have the extra money right now. It is on the evergrowing "to do" list

 

You've got me thinking and worrying now. Mine makes a little nosie after the engine has been shut off. I'll have to listen more closely nest time and do some checking. With the cold weather out I wasn't about to start messing around under the hood. Now that it's warming up I need to check a few things out.
I've suspected mine might be going bad for sometime but never could come to a real conclusion. What kind of side to side or top to bottom movement does everyone's fan clutch have in it?

So Imperial is not the great, huh. Oh well I'll give one a try as that is what we sell at work and can get for a discount and no matter now many go bad I will get another, if you work in the parts business you always get a warranty. Just return the old one and pull a new one off the shelf. What I truely would like to do if money will allow is go for the electric setup. Now that I would have to get somewhere else.

 

Hey KYFordFreak,

Mine actually had very little play in it. The thing about mine was the darn noise . . . it sounded AWFUL! It was much worse when it was cold out. If it is just a little noise, I'm not sure how worried I'd be . . . might just be one of those things that you hear because you think it's wrong . . . I've had lots of those The noise mine was making was very obvious and you could hear it from 30 feet away no problem.

I too would like the elctric setup but the wallet didn't agree at this point in time. My local dealer was pretty good. I got an OEM clutch from them for 160.00 Canadian so I was pretty happy. That was a good compromise between the jobber part and the electric setup.