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Fan Clutch Testing

Kennedy Diesel fan clutch. Purchased end of 2019. I have never heard the fan kick in.
As recommended by @Will L. I purchased a heat gun and screwed the fan clutch onto the WP shaft.
I began heating on the outer diameter of the clutch. Slowly rotating the fan to heat the clutch evenly. It finally came up to about 150 degrees on the forward side of the clutch. The bimetal spring was about 160.
I finally started timing at one minute intervals then turning the fan two blades, one minute of heating then two more blades. I did this process for about five rotations but could not get much past the 160 degree temp.
Changing to a minute and a half then moving three blades really increased the temp.
I could get the forward half to about 190 degrees, the back half to around 170 and the bimetal spring to 220 degrees.
The fan never did lock up, it remained at about the same resistance all the way through the heat procedure.
I dont know if the back half has to hit the 185 degree range in order for the clutch to properly engage.
Earlier I had contacted Kennedy Diesel about the engine running at 217 degrees and never hearing the fan kick in.
His reply was that the temp ahead of the fan clutch had to reach 185 degrees in order for the clutch to engage and spin the fan.
Any thoughts on testing the fan clutch would be appreciated.
I am thinking that my next step is going to be to lay the wrench I use for fan clutch removal onto a block of wood.
Set the nut of the clutch into the wrench then start heating the fan clutch from the back side with the butane torch and from tje front side with the heat gun and then see if I can get the entire unit up to about 190 degrees and see if it will lock up.
I could too pinch the wrench into the vice so that the fan blades would be hanging vertical, just in case that would be the position it would need to be in for proper testing.
Thought, Comments ?
 
The Thermal Spring opens a "valve" in the fan clutch to allow the "working fluid" to move via centrifugal force in the clutch to the working chamber and lock the clutch up to whatever %. The working fluid is also pumped out at a specific rate to unlock the clutch so it will unlock when the internal valve closes.

Bottom line the fan clutch needs to be spinning at ~600 RPM or so to lockup or unlock. Things happen faster at 2000 RPM.

 
Last edited:
btfarm said:
I had a satisfying experience with the Kennedy clutch on my LBZ. I recommend it.
Click to expand...
At what engine temp does You fan clutch kick in ?
I too had heard nothing but good about the KD fan clutch and so tjats what I went with.
When You first start Your truck, cold engine, can You hear the fan roaring ?
 
WarWagon said:
The Thermal Spring opens a "valve" in the fan clutch to allow the "working fluid" to move via centrifugal force in the clutch to the working chamber and lock the clutch up to whatever %. The working fluid is also pumped out at a specific rate to unlock the clutch so it will unlock when the internal valve closes.

Bottom line the fan clutch needs to be spinning at ~600 RPM or so to lockup or unlock. Things happen faster at 2000 RPM.

Click to expand...
Okay, no way of actually testing the FC when off of the vehicle then. 😭😹😹😹
 
MrMarty51 said:
When You first start Your truck, cold engine, can You hear the fan roaring ?
Click to expand...

This is a RANDOM thing called Morning Sickness. IF the fan was locked in on engine shutdown it will be on when cold. IF the ports are in a specific position on shutdown the working fluid can move into the working chamber locking it in. Generally yes, and when they randomly don't have morning sickness the AC systems on Dodge Cummins trucks explode. :facepalm:

Cardboard restricting the cooling stack is one way to test the fan clutch. No AC use and carefully watch engine temps.
 
WarWagon said:
This is a RANDOM thing called Morning Sickness. IF the fan was locked in on engine shutdown it will be on when cold. IF the ports are in a specific position on shutdown the working fluid can move into the working chamber locking it in. Generally yes, and when they randomly don't have morning sickness the AC systems on Dodge Cummins trucks explode. :facepalm:

Cardboard restricting the cooling stack is one way to test the fan clutch. No AC use and carefully watch engine temps.
Click to expand...
Oh my, that thought, about cardboard, never crossed My mind.
Like my BIL says, instead of I’ve a half a mind to ……, he says, If I had a half a mind. 😩😹😹😹
 
Well screw it. I’ll put the truck back together with what I have, minus the flow kooler pump, go ahead and run it the rest of the summer, then, after I take care of one important obligation that will be stamped down on the CC, going to get into Rock Auto and get those electroViscous fan clutch system coming.
 
The Kennedy has more of a whine at cold startup rather than the so called "morning sickness" roar I was used to. It goes away in a short time. As far as what temperature it locks, I don't know... Never really paid attention.
 
Crud! Sorry I didn’t explain that right.
This is my issue with remote helping- normally I do it with the person and in actually doing it I don’t miss steps to show that are important.
It’s like a job interview I tanked decades ago where it was on the phone and the step I missed saying was going and getting the tools out of the tool box and putting them back in the tool box when done.

you heat the clutch with it spinning. And you add heat for 1/2 minute, read temp. Heat then read, repeat. When you are hitting key temps, shut off engine and check by hand.
 
Will L. said:
Crud! Sorry I didn’t explain that right.
This is my issue with remote helping- normally I do it with the person and in actually doing it I don’t miss steps to show that are important.
It’s like a job interview I tanked decades ago where it was on the phone and the step I missed saying was going and getting the tools out of the tool box and putting them back in the tool box when done.

you heat the clutch with it spinning. And you add heat for 1/2 minute, read temp. Heat then read, repeat. When you are hitting key temps, shut off engine and check by hand.
Click to expand...
Okay, that makes perfectly good sense.
I didnt realize that the clutch had to be spinning to allow it to properly function. I figured that by heating the clutch and with the spring getting hot, it would twist and lock up the clutch. Its not so mechanical like that. 😹😹😹😹
I think that when I get the radiator topped up, I will remove the fan from the clutch then spin the clutch back onto the WP, fire up the engine and heat on the clutch, checking the temp constantly, hope that with WP temp rising and the heat gun will be enough to get the clutch to a functional temp.
Before filling the cooling system, I’m going to drill the right rear block off plate and tap it to whatever thread size the electronical temp controlled fan system sensor is, plug that hole with a pipe plug then it will be ready for the sensor install when I do the AK Dieseldriver conversion.
 
Unless I am missing a couple of things...

Am suspecting that the clutch still needs a fan on it for a resistance load.

For the sensor port, why not use the existing port in the head above #8? No drilling or tapping necessary. Just remove the plug, install an OE ECT sending unit (sending unit threads match the port's threads), and add wiring. Sure, if the motor is still in the bay that port is a real pain to access. But I can safely state that once an OE sending unit is in place, adding a wire extension is not all that hard and from there, the wires can go anywhere.
 
JayTheCPA said:
Unless I am missing a couple of things...

Am suspecting that the clutch still needs a fan on it for a resistance load.

For the sensor port, why not use the existing port in the head above #8? No drilling or tapping necessary. Just remove the plug, install an OE ECT sending unit (sending unit threads match the port's threads), and add wiring. Sure, if the motor is still in the bay that port is a real pain to access. But I can safely state that once an OE sending unit is in place, adding a wire extension is not all that hard and from there, the wires can go anywhere.
Click to expand...
Just had the inner fender removed, removed the plug and installed a temperature sending unit for a temperature gauge in the cab. I really dont want to have to go through that process again.
Although, in the thread by AK Dieseldriver about the electronic fan control, it was mentioned about a gauge that could be programmed to turn on a fan.
I’m thinking that might be a real nice option.
 
ak diesel driver said:
My second sending unit has died so I'll be moving mine to the rear of the head.
Click to expand...
To the cross over port.
When I installed the temp sender into the pipe plug port by the exhaust manifold, I was concerned about the heat. Thought about trying to build a heat shield from a tin can, then decided to just run it and see what happens.
 
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