Testing the Fan Clutch

Ducks

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Well, continuing on my list of "stupid" questions that I hate to ask but can find by searching:

Can you physically test to see if the fan clutch is working?


After driving on the freeway, I came to a stop light and the temp got very hot. I think that happened twice. Once I started driving it immediately went down. I added some coolant and it has since been running cooler than it was and there are no problems with it getting hot at the stop lights. It has been running fine for a month. Also, there aren't any leaks that I can see and the coolant level has been stable.

I will probably just replace the fan clutch but I hate to replace things simply out of paranoia. Of course, I don't want to overheat when its 110 out either. Anyways. Any thoughts are much appreciated.

:beer: Chad
 

Mace

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Typically they sieze when bad..

If it is not siezed, you can easily repack the clutch fan with the Silicone fluid..

How easily does it spin with the motor turned off?

1 revolution? 2 revolutions with a nice spin?
 

Ducks

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Typically they sieze when bad..

If it is not siezed, you can easily repack the clutch fan with the Silicone fluid..

How easily does it spin with the motor turned off?

1 revolution? 2 revolutions with a nice spin?

I've let it sit since I got home a couple of hours ago. It doesn't hardly spin. I know they aren't supposed to spin when the engine is hot and the fluid is highly viscous. How much are they supposed to spin when it is cold? Mine moves one fan blade position ahead.
 
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ducks,

some fan clutches will remain difficult to spin, even after sitting overnight. in this case, start your truck. the fan will initially roar quite noticeably but the clutch should after a minute or two disengage if it's functioning properly, and you'll know by the sound that it has disengaged. the flip side of this is to make sure that it engages once the radiator is hot.

sometimes the ambient static air isn't enough to affect the thermo sensor in the center of the clutch; it needs to have some air flow provided by the fan to do its job.
 

REKCUT

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If its not getting hot anymore then I would not mess with it. Watch it close and I would suggest getting a mechanical guage. Easy to install and inexpensive. If its your fan clutch then it should be getting hot everytime you are stopped at idle.
 
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My cruiser was getting hot at idle the rad had a small crack along the top "cap". The rad shop welded it up and soaked and rodded the core. no more overheating at idle. The shop said the crack developed because of too much pressure from overheating. The overheating was caused by the rad being all gunked up. I think I also need to replace the fan clutch. Mine comes on when on on the highway. I never hear it come on at idle.
 
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hear is my(what I use, I stole it from someone else I am sure) method to test a FC

take a piece of cardboard(or whatever), cover the rad/grill(close the hood), start up the cruiser and let it warm up.....at some point you WILL(or will not) hear the FC kick(lock up tighter) in......if its working you wont' miss the noise it makes. Now remove the cardboard and spray the rad with water.......you will hear the FC kick off.

of all my cruisers only had one lock up solid and fail, most just loose the ability to lock up when warm
 
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When I first start the engine, I can hear the roar, and then 2 to 5 minutes later, it quiets down to normal, but I've never heard the fans come BACK on. When the fans usually come back on, are they as loud as when you first start the truck? Does that mean that I need a new FC?
 
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yes, just as loud. your rig may never get that hot once running, I seldom hear mine kick on after running on my cruisers.

When I first start the engine, I can hear the roar, and then 2 to 5 minutes later, it quiets down to normal, but I've never heard the fans come BACK on. When the fans usually come back on, are they as loud as when you first start the truck? Does that mean that I need a new FC?
 

Ducks

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hear is my(what I use, I stole it from someone else I am sure) method to test a FC

take a piece of cardboard(or whatever), cover the rad/grill(close the hood), start up the cruiser and let it warm up.....at some point you WILL(or will not) hear the FC kick(lock up tighter) in......if its working you wont' miss the noise it makes. Now remove the cardboard and spray the rad with water.......you will hear the FC kick off.

of all my cruisers only had one lock up solid and fail, most just loose the ability to lock up when warm

Excellent! I'll test it when I get home.

:beer: Chad
 
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Yes its an old thread... But is this applicable to the fan clutches on the diesel engines as well?
I have a 3B and just want know what my expectations should be for this fan clutch.

Since turbo I have seen hotter engine temps (yes there is boost pressure now which increases heat). Also, I have a hard time hearing a roar that is much different than the sound of this loud engine-diesel diesel!

-thanks
 

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