How Does a Viscous Fan Clutch Work?

[@gregculverwell]

That explains why when I 1st start my car in the morning the fan runs for about 30 seconds & then disengages. Obviously the fluid has been trapped & has to flow back to the reservoir 1st.

[@MrKnutriis]

Yes - and the oil is very viscous when it is cold so it tends to drag the fan initially.

[@orbitaljellyfish808]

It all makes sense now lol

[@jf4872]

@@MrKnutriis Particularly more noticeable on a colder day vs warmer ambient temp day.

[@cristinapugh831]

Fans not moving on car

[@moriwaki1105]

Incredible Engineering 👏😮

[@thatkyleguy1289]

Well I'll be damned. Always been curious about this and now I know. Thanks a bunch!!

[@TheMrDarius]

I knew that it had its own fluid that self contained but I never understood the principles in which it acts. Very simple system. No wonder fan clutches last for years before needed to be changed. Still going to convert my Tahoe to electric fans but now I understand how the mechanical clutch works. Thank you for this. Very informative.

[@henryham5024]

These is the best description of how the fan clutch works. Thanks for explain it.

[@BigRedR-o7h]

One of the more amazing overlooked parts.

[@rorypenstock1763]

How does the fluid flow "uphill" or against centrifugal force in the return lines?

[@ddjohnson9717]

Based on this video: kzbin.info/www/bejne/hJCqnKiKnK-ladk Looks like the bimetal plate links to a piece of sheet metal that acts like a piston to suck the fluid back in. OR what I was thinking - the drive side has a specific geometry that acts as a pump all the time. so that's two possible solutions.

[@MrKnutriis]

@@ddjohnson9717 The fins in the clutch act as a pump overcoming the centrifugal force - pumping the oil back. The bimetal thermostat is opening and closing the oil entering the clutch and gets pumped back from turning. If it gets warm enough it opens for the oil and engages the clutch and keeps it engaged until the valve is closed and the oil is pumped back into the reservoir.

[@ddjohnson9717]

@@MrKnutriis yeah so like what i though: drive side has a specific geometry that can pump oil back. The fan side will have drag, and when the valve is open oil stats flow back. Very hard balancing act it looks like. Thanks for clearing up!

[@MrKnutriis]

a small valve

[@MrKnutriis]

@@ddjohnson9717 Well, it's not that difficult

[@busterscrugs]

I've always wondered how the viscous fan clutch on my E39 worked, this video was quick and made it simple to understand, thanks!

[@aminecatalyseur8281]

I want to change this oil to make it strong did u try it i have 525 tds e39

[@busterscrugs]

@@aminecatalyseur8281 the fan clutch is sealed, no way to change the fluid inside. my original fan is still working good and it has 190k miles. a new one is cheap, it's best to buy a new one if yours goes bad

[@aminecatalyseur8281]

@@busterscrugs really thank u so much..

[@jimmyboggess6534]

e39 owner here also lol

[@Ayixlia]

Your BMW can drive just fine without the fan as long your electric fan for the radiator works.

[@khaos2nd]

This technology is actually quite genius. I replace my electric fan because there were too many problems with one of these clutches and it has not failed me once so far

[@stephanparis6085]

I actually did the reverse as my fan clutch failed lol. Initially didn’t set out to remove the serpentine belt-driven fan but after replacing the water pump, radiator, hoses… and not bothering to put the mechanical fan back on, I noticed a 40+ miles increase when running without a fan. At first I thought this is impossible, a 10% increase in MPG just by removing a 15lbs fan?? I kept driving for almost a year without a fan and consistently got at least 40 more miles per tank which has a 400 mile range, sometimes as high as 45 additional miles. Now that it’s summer in TX and I can no longer drive without a fan without the motor running very hot borderline overheat, I ended up putting in a dual electric SPAL fan setup. I was a lot of work because you have to make custom mounting brackets and run wiring.. but it gets better gas mileage and is kinda cool to have an older truck with e-fans.

[@victorbatiste9834]

Changed mind 3 time and each time freon is released NO A/C 😢

[@MrBigR928]

I used one Kit Masters Horton Fan clutch rebuild kits on my 3406e Cat from Southern Electric in Conley Georgia & that was a beautiful kit & saved me a nice chunk of change too🥰👍🏿 Shout out to Dale at J&J truck repair for telling to buy it there & then he installed it for me for a great price! All together buying the reman plus install still came in under the price of a new one that wasn't a Horton Clutch! I get all my starters & alternators from Southern Electric & that's not often because they rebuild them to last👍🏿

[@316Legendary]

This is absolutely an amazing explanation. All explained simply without unneeded details.

[@davidsirmons]

Perfectly explained. Thank you.

[@V8freaks]

3:15 how does the fluid get pumped back into the reservoir? I don't get it...I would have thought that the centrifugal forces are so high, that the fluid only comes back into the reservoir, when you switch off the engine?

[@garyr7027]

That's a very comprehensive explanation, simply put yet well said.

[@kritikprasad3997]

Mate, this is one of the best educational videos I have seen. Well done, animations were amazing!

[@thepeople4142]

Impressive engineering for a $25 part.

[@GarySchiltz]

What kind of car uses a viscous fan clutch that only costs $25? I'm looking at around $400 for one for my 2003 Nissan Patrol.

[@thepeople4142]

@@GarySchiltz factory Nissan parts are ridiculous. Last one I bought for my keep was $25 at O'Reilly. Lol

[@justjoshin5140]

@@GarySchiltz if your still looking to buy one check rockauto they usually have the cheapest prices. I buy all my parts from them

[@seantbr2019]

@@GarySchiltz thats ridiculous

[@JimmyBreedlove]

@@GarySchiltz I just purchased and installed a brand new water pump and fan clutch assembly on my 1995 Nissan D21 for $48 brand new lol

[@mikeking4193]

I had no idea how these worked. The best I could come up with was so kinda magic. Thanks!

[@user-qt8zt6zg6w]

Also worth mentioning these things last forever. Ive rebuilt several engines in vehicles from the 70s 80s with over 150k miles. Have not once replaced the fan clutch

[@erickrick3901]

*Sprinter owners look over suspiciously*

[@donprather742]

Had one fail recently on my 2005 Ram 5.7. The problem presented as a high pitched whistle of all things, when the fan was supposed to engage. Took months to figure out after replacing the EGR, PCV, water pump, with no luck. Replaced the fan clutch with the water pump (and the radiator after nicking it.. oops) and voila! Noise gone and I can clearly hear the fan engage and disengage. It's actually a pleasure to hear the fan come on and off as it's a more aggressive pitch die to tow package. Also, the truck roars for a second when I start it as the fan spins before it disengages.

[@saltysteel3996]

The Humvee has a hydraulic activated fan. An extra hydraulic line comes from the power steering pump and goes to a solenoid. When the solenoid opens the hydraulic fluid pressure flows to the fan clutch and engages the clutch. It's really interesting and pretty simple.

[@TheShamiester]

Salty Steel some Toyota’s had that too. Hydraulic fans are cool tech.

[@TheShamiester]

@George Vinson I can imagine. It’s a complex system.

[@glennfrancis9031]

@@TheShamiester Yeah, I think some early '90 Camrys with the V6 had them.

[@TheShamiester]

@@glennfrancis9031 I know the ones we got from Japan had them as well on the diesel version.

[@Colt45hatchback]

My 1989 toyota celsior had the power steering fluid driven fan too. It worked well, 46°c outside, both air conditioners on, temperature remained optimal

[@joshhayl7459]

🔵 I'm still not quite clear on how the fluid is "Pumped" back to the storage-chamber when the temperature drops below the 'On' set point.

[@asvarien]

The narrator tells us that as long as the valve is open there is a continuous circular flow from the reservoir to the outer body and back to the reservoir. Once the valve is closed the circular flow stops and the reservoir is filled up and the outer parts are emptied. It's all driven by the centripetal force from the rotating parts.

[@wb3161]

Centrifugal force makes it go from the reservoir in the center outward towards the clutches and creates a drag between them

[@nssherlock4547]

@@wb3161 And.. now explain what the OP actually asked.

[@nssherlock4547]

Basically, once the central valve is shut, and the remaining fluid is spun to the outer, a smaller diameter pipe runs from the outer, back to the tank on a slight angle.The remaining air is spun out replacing the fluid, pushing the remaining fluid back to the tank, not all is sent back, some remains but not enough to drive the fan.Hope this helps.

[@wb3161]

@@nssherlock4547 I said the same thing just without adding things that aren’t there. I can tell you really don’t actually know but not everyone needs to that’s why we all know different things others don’t know. I know exactly how it works I’ve been doing this for 37 years. They also use the same principle for all wheel and 4 wheel drive within the transfer case. As the clutch assembly rotates it has no choice but to spin the fluid from the center outward and that’s what pumps it back into the center it has nowhere else to go

[@JodBronson]

WOW, I learned something new today, THANK YOU !!!!

[@karrotop]

Ok, so I understand all of that except one thing. How the hell does centrifical force manage to pump the fluid back to the centre? shouldn't it just fling it out to the outside and keep it there?

[@peculiosa]

Shear plate works as impeller of a pump. Shear plate's rotation is a bit faster then its housing, so it causes fluid to flow following plate's rotation. There is a small plastic part inside the housing next to(after) return hole, obstructing the flow. As flow is blocked by the plastic part, its pressure rises and fluid goes through the return hole.

[@peculiosa]

I just found that only some fan clutches have the plastic part. Others without the part seem to using fluid's viscosity itself for making the pressure.

[@stupidman9774]

Kelly Larsen . Better for you to play with jumping jacks than with machines.

[@carlosmejia5728]

Centrifugal...😎

[@l337pwnage]

@@carlosmejia5728 Centripetal. Centrifugal force is imaginary. :p

[@eprofessio]

I just drill holes in the clutch, run a tap and then insert some bolts. When you live in the desert Southwest it seems okay to have the fan on all the time after it breaks anyway.

[@MrKnutriis]

Mine had gone bad and I just epoxied it in place until I could replace it.

[@nairdacharles9492]

I cut even pieces from the fan blades when i did that because the fan would run at a higher speed and take too much power. Still sounds loud. I might cut off of a bit more.

[@MrKnutriis]

@@nairdacharles9492 Yes, or even better; replace the clutch. It's a $25 - 5 minute job - or 25 minutes if you're really slow.

[@mann_idonotreadreplies]

true until you use the highway.

[@lewiemcneely9143]

never had any trouble with type of clutch but really got into a crimp with a newer air operated one. Good explanation and Thanks!

[@El91637]

Thank you. Clear and to the point. Nice job.

[@jtgnc7529]

Most pneumatic fan clutches I’ve dealt with, air would be used to disengage the fan clutch, not engage it - engaged was the default position in the event of a fan clutch failure.

[@JavierMorales-pz9jd]

Hey!! Greetings from Colombia 🇨🇴 South America!! Nice video and l explanation !! Thanks

[@waleedaldikhary]

Many thanks for such a great demonstration ...

[@irishlad7458]

Thank god an actual video that exspains how they are supose to work I hope ford's have watched this Mr Ford man there not supose to spin when radiator is cold ie engine coolent temp passing through rad and when they roar when cold and spin when cold there goosed I wished all the deisel engineers and garages would have watch this it would have saved me 5 rads and stats and pumps

[@chevyls7189]

Now explain how my fan exploded

[@davidm9214]

😂

[@deandricmaxwell]

HAHAHA!

[@AMGTOM]

Extremely useful, thanks sir.

[@zt4736]

That was very well explained.

[@zenriderx]

Nice! Having mostly worked on motorcycles and VWs I was wondering what that spring was for. I was told that the viscous fluid was temp sensitive, activating the drive by thickening to transfer the power (as viscous couplers work in some all wheel drive systems).

[@DatBoiOrly]

These viscus clutches are the bomb

[@mansourkhallaf4656]

I wasn't expecting this complex👍😊

[@MichianaMan]

What direction does the bimetallic spring in the center turn when its hot?

[@titanicwhiz]

Works almost like a torque converter!

[@leonardomaddoni9870]

Yeah.. almost..

[@ghenkhoash2440]

No!

[@ethics3]

@@ghenkhoash2440 Tell us the difference Ghen

[@ghenkhoash2440]

@@ethics3 Torque converter uses fluid kinetic to transfer power, But this one uses fluid viscosity.

[@LanaaAmor]

@@ghenkhoash2440 elaborate please

[@jebysan]

Thank you so much, this gave me all the info I could have hoped for!

[@jaggass]

Can you stop Viscous fan's when the fan clutch is engaged or will you injure your hand?

[@AiOinc1]

Excellent explanation, would have never guessed that's what the spring on the front was for. These things must turn off at a pretty low temperature because the one on my truck always runs, even on a "cold" day here, about 60*F.

[@MrKnutriis]

They always runs the fan some but gradually engages as they warm up.

[@mann_idonotreadreplies]

there's always some rotation just not at full speed.

[@chriswertz1661]

I often wondered how one worked. Thank you.

[@encinobalboa]

Mercedes diagnosis question. Visco fan clutch is attached to water pump pulley. When motor is shut off and hot, fan should still be engaged and difficult to turn because belt tension is holding water pump pulley. When motor is cold, fan clutch should free wheel with little resistance. Is this correct?

[@spicyF1]

I love these intelligent mechanical designs

[@shawntravelstheworld911]

When I have viscose fan clutch go bad I just drill and tap a few holes in it then put in a few bolts to lock it up. It's not going to get much more broke. That will work temporarily till you can get it fixed.

[@brianatherton4916]

Shawn Travels The World I have did the same thing. It sounds like an airplane under the hood though

[@l337pwnage]

I guess if you lived in a really hot climate, that would make sense. You're gonna lose a lot of power and MPG, tho. They are pretty damn cheap, tho, or they used to be, and changing it might even take less time than your temp fix.

[@mann_idonotreadreplies]

@@l337pwnage cool story bro.

[@jonrinehart8402]

That was an amazing explanation

[@Qui-9]

Interesting! I used to think it was just a plate being pushed closer to another plate and always filled with thick oil.

[@kevinfrancisco1730]

Do you also need to service the fan? Do you change the oil inside too?

[@mikecorleone6797]

That explains why my friend twisted that piece the spring is connected to.. the fan quit working so he twisted that part and now it’s always working lol.. i know he’s coming up my street because i can hear the fan going from 2 blocks away

[@SGF-88]

Do you need replace/add the fluid regularly?

[@clubherbalife6292]

Ah that's good !! I ready change my fun clutch 😊 now it's work great!

[@daniel.s.stefanov]

When the engine is cold, should the fan be spinning at all? Should I be able to stop a viscous fan by hand when the engine is cold? I know I shouldn't be able to stop it when it's hot, as the clutch is engaged, but what about when it's cold?

[@dr.jenkinrivera8030]

How many ml do we need to replace the silicone oil thanks

[@jeffbrewer8810]

Excellent video. 👍

[@donens9310]

Just in process of change fan clutch on 2011 Dakota. Question does cold temp affect the clutch fluid? This morning the outside temp is -20C.

[@stevelikesrhino]

Every single Toyota truck / body on frame SUV is fitted with these clutches, making that signature whoosh even in 2022.

[@Bdady74]

Great presentation!

[@RoyRoberts-s8m]

Can an air controlled clutch fan be changed to a vicious fan ?

[@vincentrobinette1507]

I don't see what forces the fluid back to the center reservoir when the valve closes. It seems, that centrifugal force would just keep the fluid in the outer edges of the clutch. What's the failure mechanism? Why do these go bad?

[@Cj-yw8cs]

So if you install a new clutch how long does it take to release the fan? With high temperatures not above freezing and not driving alot either

[@FatPat1990]

Anyone with an 05 Aviator. If your car roars and revs high all the time change your fan clutch because it’s stuck. Four Seasons makes a great one that will give you some extra mpg.

[@AquaMarine1000]

Centrifugal force is the outward force on a mass when it is rotated. Centrifical force is the opposing force.

[@seangowan7441]

What temp would the clutch engage on a gm truck?

[@ssss-df5qz]

So how does the fluid get pumped back in if the valve is closed?

[@4by_yotaguy373]

Best explanation I've ever heard 👍 If I could thank you a million times i would

[@yoyohooyo]

Can a visions fan clutch be partly engaged for example around 200F, then fully engage around 210F ???

[@seshachary5580]

very educative. Thank you

[@tomkelly3896]

Can i run a bolt thru and lok them up ? Like we did in the 70s and 80s

[@whirlwind8825]

if you shut down a engine and the fan spins for several rotations freely is the fan clutch bad?

[@TheReginaldo1181]

very good explanation!

[@anthonymaldonado1597]

I have a 2004 Chevrolet suburban my second time changing the fan clutch and my truck still still sound like a jet plane taking off all this loud air noise would like to know if it's the fan clutch no good

[@kikecroatia1777]

This is a better option than electric option with sensor,especially when is too hot ,often electric sensor can failed and he can't engage the electric motor in the fan,big buses often have that problem,and bus engine could overheat when that happened ,because there is not enough fan cooling power to cool the engine.

[@hostilityy]

Wrong. this junk can fail too. they've been replaced by modern electric fans with separate sensors because of more reliability.

[@kikecroatia1777]

hostilityy it can be ,but i didn't have any problems with this kind of cooling system on the buses ,i work in the bus company on maintenance.We had some big troubles with sensors ,they often fail,here in Europe,main producer of the cooling systems and fans is a German company Behr,many trucks and buses have their parts.

[@kikecroatia1777]

Daver G very smart,but you must connect that switch by relay,because that fan need a lot of current.

[@BCGgaming1]

I disagree quality electric fans will greatly reduce drag on your engine thus reducing heat and friction and it being it's own independent function from the motor reduces time and money spent working on your vehicle also clutch fans have a sensor it's usually connected close to your thermostat housing.

[@wopmf4345FxFDxdGaa20]

+Kike Croatia This can fail just like electric fan / sensor. Temperature sensor is extremely simple device, it should not be prone to failure and if it is prone to failure, as a cheap component the car manufacturer could put many of them for redunancy. There probably has been some manufacturing or design error or if a lot of them have been failing at your area. When done properly, it should not fail very easily . . . Indeed this is a good system too. But difficult to say what is better. Electric has some advantages in the way how the ECU can easily control it.

[@mjsniper8247]

Question how much silicone fuid do you need?

[@wealthyblackman2655]

Toyota fan clutch! Very well defined...

[@dustyroads834]

I don’t understand how the oil goes back to the center reservoir when the valve closes centrifugal forces would keep it to the outside and keep the fan engaged even if it has a clear path back ???

[@joshhayl7459]

🔵 Yeah!.... how exactly is that made to happen?....I was wondering that myself!

[@mcguivermcguiverextreme4280]

Thanks for the information. can it be adjusted? Recently replaced mine and it takes awhile to disengage after startup, and engaged again before the vehicle can reach operating temperature ,its now causing bad fuel economy and loss of power when in its engaged . Kia k2700 non turbo ,its already under powered ,lol

[@pauldow1648]

What causes a loud roaring fan during normal engine operation. No overheating but loss of power and loud engine/fan noise. Especially in low gears. 2001 suburban 8.1 L Thanks

[@JoseLopez-eb7xh]

paul dow i have same problem,what was the amswer??

[@alfonz0010]

Time for new fan clutch

[@DaytonCarCare]

Loud roaring fan noise (when accelerating) is normal... they (fan clutch) usual sound that way when new. Fans mounted to the water pump pulley will cause some extra load on the engine. Some people do a fan clutch delete and mount an electric fan hooked to a relay that is activated at above normal engine temps. Had that on my 92 Mercedes 500SL kzbin.info/www/bejne/g2HYYpV4r9ppmskm16s

[@StrongEnough78]

That's the fan working as it should. Once the coil senses a low enough air temp the clutch will disengage and the noise stops. It's completely normal especially in hot weather. It will also do it in cold weather but will usually disengage pretty quickly once the colder air hits the clutch. If it continues to stay engaged in cold weather, the clutch is faulty. Or if you don't hear the roar at all in hot weather, it's also faulty.

[@youcanallkissmyass]

good info, thanks!

[@jpleroux5951]

Great Video!

[@joseduranjr3152]

What is Cadillac’s viscous converter clutch? What does it look like? I have a front wheel drive 1992 sedan de ville

[@ackinito]

I have noticed that my viscous fan on my truck always rotates. Is the thermoexpansion valve stuck open? Great video

[@largerification]

It rotates, because there is always some drag. That is normal. The real ghetto test is to start the cold engine, see if the fan will slow down in few seconds and if it does, try stopping thebfan with a rolled news paper... If it stops, it is good. If it does not. You need to replase the clutch Do it at your own risk...!

[@fernesal]

What's going on if the fan its always engaged?. Even if the engine it's turned off it's tight to move by hand.

[@marctronixx]

the fan is faulty and needs to be replaced. it should spin freely by hand if the engine room/ambient temp is cold

[@elmostong1865]

Great Explanation!

[@jeylful]

Perfectly explained

[@cliffcampbell8827]

I have a cooling system design idea that radically changes the shape and location of the radiator. There are a few benefits to not having a big aluminum square 3 inches thick, dependant on air flow, right behind the grill. Also, the dual fans would be about the size of you would find in a desktop computer (give or take a few inches).

[@BigRedR-o7h]

My father and I invented a transmission. So many barriers to introducing a breakthrough.

[@mann_idonotreadreplies]

cool story bro.

[@elgmichoacan818]

I guess I have a seized fan clutch in my truck, sounds like a huge vacuum, "windy", I was gonna try to oil n shimmy the coil get it loose if possible make it last more but na , 23 years working Is enough, it's time to change it

[@wesa665]

Should a cold fan/engine free spin? Should a cold engine fan still spin on start up?

[@titanicwhiz]

It will a little bit just because it is still on a rotating assembly.. there is some drag to the fan even when not engaged.

[@pepetrueno6012]

Fantastico video. Thanks

[@dannychiauyeungfui1763]

Hey, may I know if too many silicone oil will damage it? My car have slow acceleration problem after refill the silicone oil

[@seansullivan4537]

🤣

[@mikef6706]

On a Thermal Spring fan clutch: when vehicle is at normal operating temperature. Whould a magazine pressed against the fan blades and the blades stop be considered normal or is Fan clutch defective? How do you properly test one?

[@marctronixx]

if its engaged you should NOT be able to stop it by that method.

[@Leezeo]

I removed the clutch fan. And install electric fan. No more belt slip.

[@ttapia3113]

How much did it cost$$??? I own a Sierra 1500 with clutch fan n don't like it at all.

[@johndoe-yz9de]

Very cool, Big Fan.

[@preciousplasticph]

So then a simplified version could be made like the tesla turbine with a oil? since the turbine behaves in the same manner

[@alundrasrt]

Why not a direct drive ? Because in low rpm not enough Flow ?

[@abdalqadr1]

greetings for you from Iraq

[@JazzbLu]

Very informative video! I now understand how it works thank you. Can it be fixed if the clutch never engages?

[@felipecardoza9967]

My guess, because it is a sealed system, it cannot be repaired and must be replaced, much like a torque converter.

[@MrKnutriis]

@@felipecardoza9967 your torque converter shares oil with the transmission and is not sealed, nor does it work like a fan clutch.

[@MrKnutriis]

You can epoxy it shut until you can have it replaced.

[@mann_idonotreadreplies]

@@MrKnutriis obviously once installed its sealed because if not you would leak fluids.

[@mann_idonotreadreplies]

@@felipecardoza9967 Torque convertesr can be repaired but its not worth it (mass produced welded torque converters). Drag racing TCs can be repaired because its using a bolted design.

[@HighGrade_FireBlade]

So kind of like a torque converter?

[@mikef6706]

How slow should the fan spin when dis-engaged?

[@marctronixx]

should not be moving at all.. just free spinning.

[@jimjakosh2506]

'what is the difference between a thermal fan clutch and a non thermal fan clutch for the same engine?

[@doodskie999]

wait I still dont understand, why is when you start your engine cold, the fan spins or engages and blows wind strongly then after 5 minutes or if the engine heats up, it just freely spins then after a few minutes of driving, it engages again and blows so much air?

[@JayDee-xj9lu]

It could be because when the engine was hot and you switched it of, the hot liquid fell to the bottom of the friction plates because gravity. Then when you start it cold, it's thick and not viscous until it warms up and starts the cycle. What I don't get is I've had new fan clutches on a hot day and a hot engine and you can stop it with a rag and it's just doesn't seem to be doing any thing useful.

[@mnaeemkpk665]

the event of cooling fan malfunction warning pictogram is displayed on the instrument panel get the cooling fan repaired as soon as possible by a renault truck

[@andrewmontgomery8087]

Learned allot . Thanks.

[@aliveand3435]

🎉 Thankx for sharing. I need one that I am sure of.😢