Fan Clutch question ?

[bill.moulton]

While doing some other work my Mech. said he found a problem with my fan clutch and replaced it and the fan.
Sence I got the truck back the fan is real loud.
My question is , What does a fan clutch do ?
The fan seems to run all the time.
Truck is a '91 XLT EB

 

[RTStork]

I believe the fan clutch is designed to allow the fan to "free wheel" until the engine warms up. When it heats up, the clutch engages, making the fan run. The fan will still turn some while the clutch is disengaged but if you think its running full speed all the time, the mechanic might have just bolted the fan straight to the water pump pulley without a clutch.

 

[aldive]

Check the cooling fan

If the vehicle is equipped with a centrifugal thermo-static type fan clutch, it is important to spot problems before they occur. Check for wear by moving the fan blade back and forth. Over 1/4" of play in either direction could point towards excessive bearing wear. You should also turn the fan by hand. If it free-wheels or there is a rough grating feel as the fan turns, this could mean excessive fluid loss or bearing wear respectively. If any of these conditions exist or there is evidence of fluid leakage, the fan clutch should be replaced. If the vehicle is equipped with an electric cooling fan, a quick performance check can be made by turningon the A/C and checking to make sure it operates without excess vibration or noise. Also check all electrical connections for signs of corrosion, or physical damage. With the engine hot, check to see if the fan is coming on at the correct temperature and operating properly.

 

[bill.moulton]

With the motor off the fan turns freely. No mater how cold it is the fan seems to be engaged. After looking today , I see that the fan was replaced with a plastic fan.
I think that is why I get all the extra noise.
I guess my question is , When the motor is cold like just been started on a 42 Deg. morning, should the fan be
engaged ?????

BTW - The fan clutch was also replaced. I'm just wondering if it's working right.......

 

[RTStork]

The fan will engage on a startup untill the fluid in the clutch warms up some, then it will operate normally.

 

[bill.moulton]

OK, When might I Expect to see the fan NOT engaged ?
So I can be sure the clutch is working ok ???

I don't understand what the point of the fan clutch is
at all. It seems to me that if it has a clutch, there is
some condition that it should not be engaged ?

 

[Chris Jella']

Bill,
I replaced my fan clutch when I replaced my water pump and fan (cracked). I went through 2 Hayden brand, and 1 from another before finally buying a Ford OEM unit. All of the others sounded like a jet taking off and didn't kick out, even when warmed up. The Ford part, cured the noise and it works fine now.
CJ

 

[RTStork]

Originally posted by bill.moulton
OK, When might I Expect to see the fan NOT engaged ?
So I can be sure the clutch is working ok ???
I don't understand what the point of the fan clutch is
at all. It seems to me that if it has a clutch, there is
some condition that it should not be engaged ?

Ok, I did some research and there are 2 types of fan clutches, Thermal and Non-Thermal. If your clutch is a non-thermal, it will be engaged at low rpms and it will disengage at higher rpm's. Makes sense because on the hwy you don't need the fan running because the force of the wind, cools the radiator. A thermal clutch will operate as described earlier, engaging when the engine bay temp reaches a certain range. Your mechanic could have installed a non-thermal clutch. Theres nothing wrong with that type of clutch, just drive on the hwy and make sure the engine isn't running too cool and you know it is disengaging like its supposed to.