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DIY Fan Clutch mod

Bimetal strip - two different alloys bonded together - heat it and one alloy expands faster than the other, so the strip curves as it lengthens - form it into a coil with the quicker-expanding alloy on the outside, and the result is the coiled strip uncoils as it lengthens, the resulting movement in a circular motion able to perform work, such as turning the gating-valve shaft in the clutch - the hotter it is the longer it is the greater the hookup - Science 101.............
 
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I have stated this before in other threzad but I have proved that thoery. I made it from LI City/East NY all the way out to Kings Park Long Island in 90 degree heat with no fan on a Mid 80s Western Star ww/ 425 Cat haulin about 135,000Lbs(Sand boxs run heavy on LI.) Truck never broke a sweat till I got off the highway. HOWEVER this was my argument when guys here would say oh, Heaths fan, Oh Kennedys fan..etc etc. Well I had a little eye opener. My new Dodge w/Cummins diesel was pulling the berkshire mountians with about 7k worth of camper on and it was dam hot today. Runnin 65 MPH that Cummins started climbing on temps. I Heard the fan kick in (on a Cummins you HEAR it)and the temps came right down as they should so the theory of the engine fan helping at highway speeds is proven. Myth Busted.
 
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Acesneights1 said:
I have stated this before in other threzad but I have proved that thoery. I made it from LI City/East NY all the way out to Kings Park Long Island in 90 degree heat with no fan on a Mid 80s Western Star ww/ 425 Cat haulin about 135,000Lbs(Sand boxs run heavy on LI.) Truck never broke a sweat till I got off the highway. HOWEVER this was my argument when guys here would say oh, Heaths fan, Oh Kennedys fan..etc etc. Well I had a little eye opener. My new Dodge w/Cummins diesel was pulling the berkshire mountians with about 7k worth of camper on and it was dam hot today. Runnin 65 MPH that Cummins started climbing on temps. I Heard the fan kick in (on a Cummins you HEAR it)and the temps came right down as they should so the theory of the engine fan helping at highway speeds is proven. Myth Busted.
Click to expand...

Once again Something amiss with your fans in your rigs then, when mine comes on, you HEAR it, and FEEL it. Hell you can even feel the heat push through the firewall.
 
Ironically, Heath sent me another one to try on my Tahoe...sob sob sob...
Well might as well. That would be a bitch if the truck towed perfect. It would also be very Irish luck.
 
Acesneights1 said:
.. so the theory of the engine fan helping at highway speeds is proven. Myth Busted.
Click to expand...

..ya might want to see if that '02 radiator needs cleanin'...):h

..could get into the aerodynamics of that flat nosed Western Star vs. the round nosed dodge..average dynamic pressure over the couple of acres of radiator on the W.S. vs. aerodynamic diffusion around that pretty grill..:conehead:.... nah.

Yeah, when you're not loaded they'd rather the air went around instead of through. Less drag that way. The fan did what it's supposed to when the air temp came up behind the rad. Kinda like the guys with the plows, when yer breakin that much wind ya need more sucktion. :D

(..'nuther martini please?...)
 
Matt Bachand said:
Unless you have a 9' x 3' square piece of Steel hangin in front of the radiator
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I didn't realize you had a plow, they're kinda rare here in Baton Rouge :D

Could a square be cut out to allow airflow when plow is not in use,
and tabs welded on cutout piece to allow you to bolt it back on when in use?
 
Acesneights1 said:
I have stated this before in other threzad but I have proved that thoery. I made it from LI City/East NY all the way out to Kings Park Long Island in 90 degree heat with no fan on a Mid 80s Western Star ww/ 425 Cat haulin about 135,000Lbs(Sand boxs run heavy on LI.) Truck never broke a sweat till I got off the highway. HOWEVER this was my argument when guys here would say oh, Heaths fan, Oh Kennedys fan..etc etc. Well I had a little eye opener. My new Dodge w/Cummins diesel was pulling the berkshire mountians with about 7k worth of camper on and it was dam hot today. Runnin 65 MPH that Cummins started climbing on temps. I Heard the fan kick in (on a Cummins you HEAR it)and the temps came right down as they should so the theory of the engine fan helping at highway speeds is proven. Myth Busted.
Click to expand...

Also, my temps do go down when the fan kicks into gear, it just happens "way too late."
 
Got my new Heath Fan today. Gotta put it on and go for a tow. The irony will be of course as my new Dodge sits in the shop with trans problem the Tahoe will now, not overheat.
we'll see.
 
Pics Finally.

Wasn't able to take a pic of the straightened tab, but you'll figure it out.
 

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Also helps if that bimetal coil is not caked with grease'n'dirt'n'stuff, which can insulate it from direct thermal response, thereby raising the temperature of engagement even higher than stock

- remove the oem RTV blob to release the tab

- carefully pry\pull the vertical tab of the coil from the aluminum slot

- carefully bend the tab at your desired calibration, closer to the end of the tab

- now, carefully straighten the original bend such that your newly-bent vertical tab fits securely into the slot

- note that you have rotated the gating shaft, which lowers the temperature of engagement

- use Permatex RTV to bond the recalibrated tab into the slot - black or gray or orange or blue is good, can be color-coordinated with your truck's paint scheme

Try it...you'll like it.................
 
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matuva said:
So, do you have to bend it so as to make the strip shorter or longer ?, the coil is then more or less tight ?
Click to expand...

Basing my interpretation on GMCTD's explanation, the strip would be a bit shorter and the coil would then be a bit looser.

3/8" shorter? 1/4" shorter?

I'm going to do mine soon.
 
You're making the original tab-strip shorter, adding length to the coil winding, thus rotating the shaft such that the internal gates are more closed - this procedure is sometimes called 're-clocking' the clutch

Fer-eggs-ample-test - take the significant other's electric hair-dryer (while that other is on a shopping errand or the cell phone, for conjugal integrity's sake), plug it in, turn it on DRY\equiv, point the hot business-end at the bimetal coil, noting the reaction and resultant directional rotation of the shaft from that reaction as temperature rises - don't even dally, here, as that 'other' may return unexpectedly, reducing the timing required to return that hair-dryer to it's pre-assigned location elsewhere, far from the garage.................
 
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mfgguru said:
Pics Finally.

Wasn't able to take a pic of the straightened tab, but you'll figure it out.
Click to expand...



Thanks for the pics. Done that today on my fan clutch (I bent the tab about 5 mm later as OEM).
Still waiting for the 180°F thermostat, which I ordered from KennedyDiesel, so I couldn't take the truck for a testdrive. If the thermostat is here, I will install it asap and then I'll post my results.


I knew that the later models got a different flange like yours (mine is the older 4 bolt style), but it also seems (according to your pics), that the fan blades are different too - compared to mine.



Cu,
Sven
 
Don't fergit to run the engine awhile to purge and fill the coolant passages, shut it down, let it cool, pop the radiator cap and top-off the radiator with 50\50 mix - neglect of that procedure has caused many an incident of overheating after coolant system rework
 
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This mod should work in reverse also...Correct?

I need to increase "disengaugement" time....as the "Kennedy clutch" seems to never want to unlock.
 
Oooh, Louis, I'm not sure I'd be messing with a Kennedy clutch. If you screw up a worn-out GM clutch, you can always go tell yourself you needed a new one, anyway.
 
Other than that precautionary note, it will work with any viscous clutch with external bimetal thermostat - I had one with a vernier-adjust setup on it, but gave up on the idea due to inertial mass imbalance
 
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