DIY Fan Clutch mod

[jmiller]

Guys, I'm hearing too many talk about fan clutches to help the cooling at 60-75 mph. At freeway speeds your fan clutch shouldn't need to be doing squat. If you're having cooling problems at that speed you're not transfering heat well enough. Throw in some Red Line Water Wetter, bleed the air out of the top hose, clean the rats nest from between the rads, or something. My Kennedy clutch kicks in (KICKS in) when I'm going slow; that is with little or no air speed. Once I get some air speed I can feel and hear it unload. On the freeway it's freewheeling even with my trailer on and the ECT (scangauge) stays in the 190s. It was in the 90s here on Saturday and I never saw over 200* with the trailer on.

Mike

In 10F weather, a raised plow can get an empty truck to exceed 215F at 70 - 80 mph. Then the stock fan kicks in fully and pulls the temperature right down. But at 215, its a little too hot for comfort.

The blade can actually pull a vacuum between the blade and radiator. Before adding a snow deflector, I had to run the blade an inch off the ground on the Interstate to keep the temps down. The blade hit the ground on ever bump and expansion joint.


This is definitely on my list of mod's.

Thanks to GMCTD, and mfgguru for remembering the original post.

John

 

[Matt Bachand]

NOW, after the mod, I can hear it engaging, but no before. I never heard it before. I thought about thinking a new clutch before, but now, I know, I don't need a new clutch. I didn't needed a new one, I just needed the clutch mod.

BTW :

I don't care about loosing some horspowerand using a bit more fuel, while the fan is engaging earlier, cauz it is much more important for me that this "damned" truck doesen't overheat - what it does anymore now.


Cu,
Sven

So true, so true.

 

[Matt Bachand]

In 10F weather, a raised plow can get an empty truck to exceed 215F at 70 - 80 mph. Then the stock fan kicks in fully and pulls the temperature right down. But at 215, its a little too hot for comfort.

The blade can actually pull a vacuum between the blade and radiator. Before adding a snow deflector, I had to run the blade an inch off the ground on the Interstate to keep the temps down. The blade hit the ground on ever bump and expansion joint.


This is definitely on my list of mod's.

Thanks to GMCTD, and mfgguru for remembering the original post.

John

I agree with the plow problems. I can't wait till winter to try the fan clutch mod. kicking on at 215 is too late in my book.

 

[Matt Bachand]

I agree with the plow problems. I can't wait till winter to try the fan clutch mod. kicking on at 215 is too late in my book.

Doing this Sunday. Will be hooking plow up in a few weeks (after shock upgrades) to start working on it. Will post results. I'm going to loosen up the coil 1/8th inch. Making the 'leftover' tab 1/8th smaller. I use to engage around 210 (little over) on my cab gauge. Can't wait to see when it engages now.

 

[Matt Bachand]

Moved mine 1/8th in looser coil. Took it on a highway beat, and got the temp to raise a tad over T-stat but no fan engagement, which is good. No scanner yet to pinpoint temps. Will report back when plow is loaded in a week or 2, to see if it enganges well before 210 as I would like.

 

[Matt Bachand]

GMCTD Your problem with making an adjustment screw for the viscous clutch was it would be out of balance.

What if that screw was in the dead center of the clutch?

 

[dangerousdave]

On the counterweight for the vernier adjustment, why not add a small wheel weight to the opposite side (solder or braze it on) and grind it down 'till balanced J U S T right?

Cleaning the bimetal definetely helps cooling, just like cleaning the rad in and out helps.

 

[Matt Bachand]

I'll be grabbing my plow today hopefully to test drive my adjustment and see if it comes on around 205 as desired.

 

[Missy Good Wench]

The mid 80's GM Pickups and Burbs (Gassers) had a fan clutch that would come on fairly early if the engine was working at all.

The Fan would Howl like hell and this resulted in many complaints to the dealers from consumers "Whine"

I had a shop at home back then and one fellow had an 88 Burb 4x4 that he swore the tranny was slipping in once it was warm and pulling on a grade.

Local driving would not bring on the condition.

We even ripped the tranny apart looking for the cause of this RPM spinup.
The tranny was perfect.

I installed a shift kit in the tranny just because it was a good idea.

I figured that the issue was over.

Two weeks later the fellow is back and "PISSED"

I kept the truck for a weekend and drove it to the mountains.
As regular as clock work, hit a hill and work it a little and the fan would hook up and Howl until the engine temp fell off a little bit.

Fan would come on when the engine temp hit about 200F (190F stat)

I also watched the tach and the RPMs of the engine never changed.

Informed the customer but he insisted that I do something as that noise was not acceptable.

We flopped around with that mess for several months before he was happy.

I certainly would love to see a clutch on a 6.5 work that good.

The rig I spoke of had a 9 blade steel fan with the HD clutch
350 gasser, 2500 Burb 4x4 with tow package.
Rig had 45K miles at the time.

I have thought about making an adapter to install that fan and clutch on the diesel.

The early serp drive gasser setups for the 454 were also very similar and engaged at fairly low temps.


Missy

 

[Diesel -T]

Had an 84 Motor Home with 454 . First time the fan engaged (really hot day on a hill it nearly gave me a heart attack. Kind of wish sometimes I had that setup in place of 6.5.

 

[Matt Bachand]

COMPLETE AND UTTER 1000%%%%% SUCCESS!!!!!!


Loaded up the plow, drove around regular routes where consistant 30-40mph flat grades would normally cause temps to climb well over 210 if I did not back out of it...

Well, at least a complete notch before 210 on my temp guage, and sure enough, I heard the little whine start up! I was completely smiling ear to ear. Once the fan is engaging, The faster I drove, the faster it cooled.

As it went back to t-stat temps, I routed around and took another route, same thing, without changing driving (getting into it once engaged) It got a notch from 210, and i heard it whine little bit (normal low rpm driving in 3rd 1800-2000) I didn't get into this time, and it never went above that point, and as I approached the stoplight it was closer to t-stat spot.

Even better, probably due to the fact the plow blocks the cool air, it lingers a little bit engaged, which is absolutely perfect, I didn't even notice the power difference, but temps stopped rising dead.

I adjusted 1/8th inch. If I have the clutch off again, i'll go it another 1/16th for a total of 3/16th movement.

THANK YOU SO MUCH GMCTD For informing us of this. Sending him a PM just in case he misses this thread. I am so happy about this only you guys understand.........

This was the one area where I would literally worry my ass off, waiting for fan to engage.

This was also when temps climbed last year and i had a valve failure, waiting for fan to kick in to cool her off.

Needless to say with a 97 block, I worried EVERYTIME i had plow on.

Not anymore.

I am so happy.

 

[Veg_Out]

Well done Matt!

 

[buddy]

The most satisfying mod is usually the free one

 

[Matt Bachand]

The most satisfying mod is usually the free one

Free or not buddy, you have no idea (well, maybe you do) how good if feels to be able to drive over the road with the plow on without STARING at the temp guage, letting in and out of throttle trying to let the fan clutch engage....

Worrying about should I pull over and cool down? Keep going? Crack my block? ARGHGHGHGH!!!

No more...

FWIW my fan is OEM replacement from GM only 2 years old.

So happy about this mod. Only you guys can understand.

It was never an issue plowing, thank god, but just traveling from point A to point B.

 

[turbovanman]

I've done this on 2 customer vehicles, one has a 98 and towed his 5th wheel to Vegas and back, thanks for the mod, :thumbsup::thumbsup:

 

[Matt Bachand]

Loaded up the plow and took it around with the scanner. Was kicking on around 205 or so. Not bad.

Went up a highway pull for a quick exit, and temp in gauge went to 210, Scanner read 217. Too hot for me.

I adjusted it another 1/8 inch.

Drove around for 2 days, fan never engaged without plow.

Loaded plow and dropped it off at my welder, with scanner of course.

Fan now engages with the plow on right around 200df.

Absolutely perfect. My 195 T-stats maintain idle/regular driving at 190-192. I feel like I just added years to my block.

Also IAT's on that 217 (where the fan never actually engaged, keep in mind Plow plays all sorts of airflow games), IAT's were up over 200. With the fan engaged, IAT's were under 150.

I also modified the lenght on my plow lift chain so when its raised the triangle is pointing upward around 60 degrees, thus being its own slight air scoop pointing right to the center of my radiator. If that overcomes the wind tunnel effect off the plow, who knows. I'll find out when the snowflakes are falling!

 

[ak diesel driver]

Might pack the radiator full of snow too.

 

[Detroit Dan]

Matt, I've seen people mount a piece of plexiglass or lexan on the triangle, so when it's angled up it directs a larger chunk of the air down toward the grill.

 

[Detroit Dan]

BTW, I heard my fan running when i started my truck yesterday. It had only warmed up for a minute or so, I usually let it run longer (remote starter) Drove a 1/4 mile and it went off. Never noticed this before, and the fan never comes on unless I'm really working the truck. Does this mean the fans on it's way out?

 

[Matt Bachand]

BTW, I heard my fan running when i started my truck yesterday. It had only warmed up for a minute or so, I usually let it run longer (remote starter) Drove a 1/4 mile and it went off. Never noticed this before, and the fan never comes on unless I'm really working the truck. Does this mean the fans on it's way out?

Not sure. Mine someotimes does after shutdown heatsoak... Then goes off with a little RPM...

Take it off, clean it up really good. If its adjusting late, loosen the coil a bit.

I have no need for the plixiglass or any other modifications now, my fan kicks on so fast and early with the plow on i can really get on it and drive it like its not even there...