How to test fan clutch?

[unioncreek]

I realized the other day that I haven't heard my fan kick in lately.  When the truck was cooled off I grabbed the fan blade and the was quite a bit of resistance. Wouldn't spin freely at all. I haven't had any heating issues, but was wondering if there was any other way to test it.

 

Bob

[JAG1]

There is always some resistance even when cold on a properly operating fan. You want to look for bearing play also. That's all I know about them at this point.

[unioncreek]

I check for any play in it this evening.  I'm wondering if it's always engaged and that's why I don't ever hear it come on like I have in the past.

 

Bob

[dripley]

If it was engaged you should hear it. If you keep spinning it with your hand it should start freeing up the more you spin it as the fluid starts getting dispersed. Mine does. I very seldom hear mine come on unless loaded and climbing hills in the dead summer. Sometimes I can hear it run on cold start up until the fluid gets dispersed.

[unioncreek]

Checked out my fan clutch tonight. No play or any sign of leakage.  Started the truck and run it up to 2K rpm for about 5 minutes, got out and stuck a rolled up magazine into the fan.  It stopped right away and free wheeled.  We're headed out camping with our fifth wheel on Friday so I'll see if I can hear it coming on.

 

Bob

[015point9]

1 hour ago, unioncreek said:

Checked out my fan clutch tonight. No play or any sign of leakage.  Started the truck and run it up to 2K rpm for about 5 minutes, got out and stuck a rolled up magazine into the fan.  It stopped right away and free wheeled.  We're headed out camping with our fifth wheel on Friday so I'll see if I can hear it coming on.

 

Bob

 

When you first posted I thought maybe good idea to check mine out. Most I can spin mine around with little bit of force is about 3 turns max.

 

Maybe I'm looking at wrong thing in manual?????

 

VISCOUS DRIVE...  If the fan assembly free-wheels without drag (the fan blades will revolve more than five turns when spun by hand), replace the fan drive. This spin test must be performed when the engine is cool.

 

(That's all I know... I thought they were controlled with actual fan clutch via wire to some kind of temp switch.)

Edited July 3, 2018 by 015point9

[dripley]

4 minutes ago, 015point9 said:

 

When you first posted I thought maybe good idea to check mine out. Most I can spin mine around with little bit of force is about 3 turns max.

 

Maybe I'm looking at wrong thing in manual?????

 

VISCOUS DRIVE...  If the fan assembly free-wheels without drag (the fan blades will revolve more than five turns when spun by hand), replace the fan drive. This spin test must be performed when the engine is cool.

Mines in no danger doing 5 revolutions. Mine won't do 1/4 revolution when first moved on a cold engine.

[IBMobile]

This is how I test a fan clutch.

 

Visual inspection:

Is there any staining on the clutch housing to indicate a fluid leak?  There should be no leaks.

Is the thermostatic coil spring still attached to the front of the clutch and not broken/cracked?  

Is there any play in the center of the clutch and the mounting nut?  There should be no play.

Does the fan blades spin freely with little effort, some effort, or great effort?  If with little or great effort the fan clutch is bad. 

Is there any play/roughness in the fan pully bearing?  There should be none.

Check the condition of the fan blades.  There should be no cracks or pieces missing.

 

Operational inspection:

Run engine until thermostat is open.  Drive if needed.

Now with the vehicle stopped and brake set,  block the air flow over radiator, I use cardboard.

Bring the engine speed up to 1500+ RPM and hold it there.

If there is a roaring sound at this stage of the test then the fan clutch is locked up prematurely and should be replaced. 

When the temperature gauge indicator needle moves to the right of center and is over the 0,  remove the cardboard and keep the engine speed at 1500+ RPM.

The sudden rush of hot air will engage the fan clutch very quickly, about 30-45 seconds. You will hear a 'roaring' sound as the fan clutch engages and draws large amounts of air over the radiator.  The temperature gauge should move back to the center position and the roaring sound subside as the coolant temperature returns to normal.

 

If there is no roaring sound and the coolant temperature does not decline,  reduce engine speed to idle then turn engine off.  Fan clutch is not locking up and should be replaced.

 

I've seen people check the fan clutch operation by sticking a hose, rolled up paper or some other soft material against the fan blades while the fan is moving.  I don't recommend this type of test.  If the fan clutch is not engaged the fan will stop spinning when the outside resistance is brought to bear.  If the fan clutch is locked up the fan will kick out what ever is put against it and could cause damage or injury.  

[Mopar1973Man]

7 hours ago, IBMobile said:

I've seen people check the fan clutch operation by sticking a hose, rolled up paper or some other soft material against the fan blades while the fan is moving.

 

Like me...

 

Our fans normally don't lock up fully till about 205 to 208*F coolant temperature. The has to sustained temperature to get enough heat on the thermostatic coil to pull the fan to lock up fully.