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I have noticed that when I start my truck the fan starts spinning and continues to spin while the truck is warming up. If it is operating properly should it not come on until the truck warms up, the spring expands, and engages the clutch?

Do I understand correctly how this is supposed to work? Just wanted to see if it was broken and needs to be replaced.

Thanks in advance....
 

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I have noticed that when I start my truck the fan starts spinning and continues to spin while the truck is warming up. If it is operating properly should it not come on until the truck warms up, the spring expands, and engages the clutch?

Do I understand correctly how this is supposed to work? Just wanted to see if it was broken and needs to be replaced.

Thanks in advance....
I think its normal, mines does do too, but I could be wrong. So this is a bump for you. I have hear that when the clutch engages makes a clear different big sound that you cant miss it. I have never hear it, and I live in a warm wheater, this trucks has a very good coolant system.

:ford:
 

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I may be wrong but I believe that our fan clutch is a viscous clutch. It will move with the motor but not nearly the speed of the motor over idle. As the fluid heats it will become more and more a "solid" and lock the fan in sync with the motors rotation. It sounds like a hurricane when it's doing its' job though. Also sucks up about 50hp when working as well. The fan generally doesn't wear in the locked up position but the opposite. When worn it'll just freespin with no lock-up
 

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It is normal for a viscous fan to be fully engaged when starting a cold engine and after the engine starts warming up the fan will slow down until the air coming through the radiator gets warm enough to engage the fan again. One other thing to look at is after shutting down a engine that is at full operating temp the fan should not continue spinning more than a couple of seconds after the engine stops.
 

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how to test the fan clutch:
Spin the fan blade by hand. A light resistance should be felt. If there is no resistance or very high resistance, the minimum and maximum fan speeds must be checked.
Here is a form to check:

Crank the vehicle. Take a broom and use the bristle end to try and stop the fan. You can stop any of them even with a good clutch so that’s not the part your looking for but if it seems like it doesn’t want to stop to the point its scaring you then stop there and rest assured the fan clutch is fine.

If it does stop don’t count it as bad yet. What you want to see is how fast it spins back up when you pull the broom bristles off of it. If it seems to slowly start spinning again then the clutch is bad. If it starts back to spinning almost instantly it’s a good clutch. Bad clutches also don’t pull on the broom when stopped. It’s like it’s not connected at all.

Also for the record for the flaming I’m sure I'll catch from this, you don’t just RAM the broom in there either. Use the brush part to slow the fan down till it stopped or refuses to stop easy.

Anyone that comments after this with anything about "id never do this" or that’s crazy, etc. Its been used for years by mechanics to test fan clutches and if you have old enough service manuals "pre 80's era" its in there as a test method.

When it kicks on, you will clearly heard a different big sound.
 

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I think this is more cientific
FAN CLUTCH TEST
NOTE: The following test does not apply to the 6.0L diesel. For the 6.0L diesel, refer to the Powertrain Control / Emmisions Diagnosis (PC/ED) manual.
Spin the fan blade (8600) by hand. A light resistance should be felt. If there is no resistance or very high resistance, the minimum and maximum fan speeds must be checked as follows:
Fan Clutch Test — Minimum Speed Requirement
Use a suitable marker to mark the coolant pump pulley (8509), one of the fan blade retaining bolts and the crankshaft pulley (6312).
Connect a tachometer to the engine.
Install a throttle adjusting tool.
Connect the Digital Photoelectric Tachometer.
WARNING: To avoid the possibility of personal injury or damage to the vehicle, do not operate the engine until the fan blade has been first examined for possible cracks and separation.
Start the engine and run it at approximately 1,500 rpm until the normal operating temperature has been achieved.
Operate the strobe light at 3600 rpm for 7.3L diesel engines, and aim it at the coolant pump pulley. Adjust the engine speed until the light flash and the coolant pump pulley mark are synchronized.
Aim the strobe light at the fan blade bolts. Adjust the strobe light until the light flash is synchronized with the marked fan blade bolt (the fan blade appears to stand still).
The fan blade speed must not be greater than 2,000 rpm on 7.3L engines.
Turn the engine off.
If the fan blade speed was greater than 2.000 rpm on 7.3L diesel engines, install a new fan clutch (8A616).
Fan Clutch Test — Maximum Speed Requirement
Perform Steps 1 through 5 of the Fan Clutch Test—Minimum Speed Requirement.
NOTE: The temperature of the air hitting the fan clutch should be above 96°C (205°F) for maximum fan speed.
Block off areas on each side of the radiator in the engine compartment and the front of the radiator grille (8200). This will raise the temperature of the air striking the fan clutch and should cause the fan blade to operate at maximum speed.
Place the climate control function selector switch in the MAX A/C position and the blower motor switch in the HI position.
Adjust the strobe to 3,600 rpm for 7.3L diesel engines.

WARNING: To avoid the possibility of personal injury or damage to the vehicle, do not operate the engine until the fan blade has been first examined for possible cracks and separation.

Start the engine and adjust the engine speed until the strobe light flash and the coolant pump pulley mark are synchronized.

Aim the strobe light at the fan blade retaining bolts. Adjust the strobe light until the light flash is synchronized with the marked fan blade bolt (the fan blade appears to stand still).

If the fan blade speed is less than 2,850 rpm on 7.3L engines, install a new fan clutch.
 

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Ahhh the old broom trick. Never let me down.
Ford procedure for testing fan clutches is a royal PITA, not to mention loud and requires a way of electronically manipulating the engine rpm.
 

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It is normal for a viscous fan to be fully engaged when starting a cold engine and after the engine starts warming up the fan will slow down until the air coming through the radiator gets warm enough to engage the fan again. One other thing to look at is after shutting down a engine that is at full operating temp the fan should not continue spinning more than a couple of seconds after the engine stops.
I agree 100%. This explanation is probably the best I've seen. Before I replaced mine, it continued to spin and spin and spin after the engine was shut off. After I got the new one on and started the truck, VERY obvious difference..... you really hear the noise of the fan engaging, and eventually quiet down.

If you DIY and don't want to spend a ton of money, check out RockAuto.com. They had great prices when I got mine earlier this year. And, check out/rent a wrench set from your local parts store to get the nut loose. Makes it a piece o'cake to replace the fan clutch.

Like this: Performance Tool W89400 - Wrench Set | O'Reilly Auto Parts
 

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Discussion Starter #9
Great stuff guys, and I will have to try the broom test. I did notice that mine was spinning for just a couple of seconds after I shut down.

One other question: is there a point at which this fan would "switch" off? Meaning that if I am driving down the interstate in cold weather and the fan may not be needed, will it disengage? I believe that some have springs that expand and contract, and engage and disengage. Do I have this right, but maybe these viscous fan clutches don't work this way?

If it is on most of the time, are you losing horsepower?
 

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While your in there screwing around why not put in a 6.0 fan, it has more blades. Read somewhere its a direct swap over.
 

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Great stuff guys, and I will have to try the broom test. I did notice that mine was spinning for just a couple of seconds after I shut down.

One other question: is there a point at which this fan would "switch" off? Meaning that if I am driving down the interstate in cold weather and the fan may not be needed, will it disengage? I believe that some have springs that expand and contract, and engage and disengage. Do I have this right, but maybe these viscous fan clutches don't work this way?

If it is on most of the time, are you losing horsepower?
Yes, a properly working fan clutch will engage when more air is needed across the radiator, and disengages when it's not needed. On startup, if you're not hearing a noticeable, steady "whoosh" which indicates that the fan is engaged (like it should be on startup) and eventually quiets down (should only take a couple of minutes), your fan clutch needs to be replaced.
 

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Discussion Starter #12
Thanks to all...much appreciated.
 

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By 'disengage' do you mean stop spinning altogether?
There should never be a point where the pulley is turning and the fan is stationary. The fan clutch doesn't have a full disengage that isolates the fan from the pulley. Some energy will still be transmitted, although the fan will rotate much slower than engine rpm. A fan clutch operates similarly to a torque converter, using silicon fluid as a viscous coupling to transmit energy from the pulley to the fan. When the fluid is cool the majority is stored in a reservoir allowing the clutch to slip relative to the water pump pulley. As it heats up, a thermal spring expands and opens a valve which drives the clutch at a rpm closer to that of the engine.
 

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Of course it doesn't stop spinning altogether..... othewise, "what you said".
 

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NRA, wasn't directing that comment towards you.
Just making sure the original poster wasn't replacing the fan clutch due to the assumption it was bad because it was constantly spinning. Those little buggers aint cheap.
 
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