How Does a Viscous Fan Clutch Works in Your Workhorse Chassis With a 8.1 Vortec Engine W8002567 

I have over the years heard all kinds of theories as to how these things worked. NOW WE KNOW!! Thanks Kevin

I have always wondered why the fan clutch is engaged for a bit of time during a cold start. Now I know, thanks, Kevin

I used to work at Borg Warner and made fan clutches back in 2002.

Very interesting Kevin! Thx for sharing !! Scott

It's a centrifuge in constant motion. It seems that by design it will eventually break down the oil components and cause them to leak out. Good forensics!

Silicone oil is used because it stays thicker at high temperatures. In a pinch once, I drilled and tapped a hole in one of these and mixed up some silicone brake fluid with molykote 111 silicone grease until it was the right viscosity, then squirted it in the hole with a syringe. Worked like a champ. They typically leak all the fluid out around the control shaft under the spring. If you look, the springs are always oily and covered with dust on "worn out" fan clutches. Seemed like there was a little evidence on this one.

Wow, thanks Kevin, I also wondered how the fan clutch works, very informative, thanks for taking the time. I also noticed the roar of the fan when the engine is still cold and wondered about that, I believe you are correct that the oil drains out.

You just saved me a pain in the @$$ with your explanations! Amazing mechanisms

Great dissection and I think you have discovered why they cost so much.

Hey!! Greetings from Colombia South America!! Nice video !!

Lets make this official... Yes, I did enjoy the video. Now as you were saying, around 70 to 80 000 miles, it's normal for it to fail. But, you've gotta figure also where did this W22 live most of it's life. If it was down south, in torrid heat, contrary to us, up north (Canada), these conditions are also a big factor. Thanks for the schooling 😉🙂

Very interesting, thanks for sharing!

Great video. Thanks for the info.

Best explanation I have seen by far.

very useful demonstration thank you

This morn i cut the coil spring with a dremel....and then was able to turn the valve to open position.....fan is now engaged...temp is down 20 degrees🤠🤓😎🤗✌✌✌✌

Fantastic video.

Thanks Kevin. As always a very informative video. It would be interesting to see what differences there are between OEM and aftermarket products.

Good info I subbed have a 05 endurA super c with the 8.1

I still have the scars on my left arm from a viscous fan attack in 1992. Bit me real good when I leaned in to work on the carb while it was running. 😁

My 1990 LJ78 400k, auto , has a viscous fan.. I changed the radiator and thermostat bout 10 years ago , when I tow my trailer with the 1200kg buggy over the hill on way to coast the temp would rise slightly , but the temp light for tranz would light up, I just pull it down a gear, run the revs at bout 3500, after bout five minutes it would go out.. I can hear the fan working.. holding that ratio going down the other side, I hear the fan noise fad away.. The radiator caps these day are junk.. The stem the attaches the spring and seals etc come lose on the top, allowing air to be drawn into the radiator as the engine cools . Radiator should be full to the seal when you check it before first starting it..

Ok...i nust cut the coil spring with a dremmel tool....and was able to turn the valve to let the fluid flow....its workin...but i assume the fan will stay mostly engaged now ....thats ok cause im in s. Az...temps are 100 to 110.....i will turn valve closed in oct ....and see if it operates as normal when air temps drop✌✌✌ good luck

I changed my fan clutch of my fj cruiser for a new one. I see that when cold the blades move not so freely and when hot it gets much harder. I have seen that the engine makes more effort and has lost acceleration. Could it be that the hardness of rotation of the blades influences the motor to slow down?

S0, where can we drill a port to fill it?

What happens if I bore it and lock the fan permanently to the axe? Would this solution destroy the belt?

Did the spring just pop up off the valve easily...or did you cut thru a tac weld of some sort? Thx im considering popping mine off and leaving the valve open in az summer heat...tacoma running at 220 degrees...non towing😲🙈😲🙈😲