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Thread: Fan / fluid coupling (fan clutch)

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    Fan / fluid coupling (fan clutch)

    Noticed my fluid coupling assembly (fan clutch) spins independently from the water pump pulley. Is this normal? Should the fan spin without the pulley moving? May be a dumb question...sorry.

    Thank you.

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    Re: Fan / fluid coupling (fan clutch)

    The fan clutch will allow the fan to spin at a different speed than the water pump. There is a bimetal thermostat coil on the front of it. When it gets hot (around 200 deg F) this coil moves enough to start changing the valving inside the clutch. It's a variable change that's linear to how hot the t-stat coil is. Typically the fan will spin whenever the engine is running simply due to centrifugal force, but unless the thermostat is engaged it will spin much slower than the pulley (freewheeling). When the temp gets high and the valving changes, the silicone goo inside gets restricted (this makes the clutch engage). The more it engages the faster the fan spins and the faster it spins the more air it will move. When more air moves there's more heat transfer from the radiator to the passing air. As the air gets cooler, the valving opens and the fan begins freewheeling again. The purpose here is to only turn the fan on when it's needed. Fans that run 100% all the time rob fuel economy and horse power. They also make a lot of noise. A correctly functioning fan clutch is a wonderful thing

    Due to the placement of the radiator and the air flow characteristics in the engine compartment, the clutch fan is one of the most important parts of the cooling system. Due to the viscosity of cold silicone, it's normal to hear the fan engage for the 1st minute or so when the engine is cold. After the silicone is warmed up you shouldn't hear it engage again until your temperature needle hits about half way on your temp gauge. Then it should run briefly and the needle should return to about 3/8 of the scale. It may not run at all during the winter, but it should definitely see some action in the summer.............especially if you have working AC. Here's some pics of the internal workings of a clutch fan.

    Here's the bimetal coil


    Here's a bimetal coil reacting to heat


    Here's a clutch that's opened up


    The black propeller looking thing is directly attached to the bimetal coil. The coil moves this when temperature changes. Depending on it's position, it can block or allow the silicone's passage through the slots in the disc I'm holding.

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    Re: Fan / fluid coupling (fan clutch)

    Awsome info Tim. Thanks. That clip of the coil reacting is great. I got worried when I noticed for the first time the fan spun without any other mechanics moving. I think I read in other thread somewhere someone was fixing their fan clutch because the fan wouldn't roar on a constant basis. Good to know now, it shouldn't be.

    Any tricks or tips to inspecting while still connected and a cold engine?

    It's going to be several days before engine is running and I have fan and belts back on.. In the past, I haven't had temp issues, I have working AC, & I don't think I have any problems here now. But wanted to check if possible while I have things opened up changing belts.

    Thanks

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    Re: Fan / fluid coupling (fan clutch)

    A correctly working fan clutch will roar for a few rev's while cold, and roar again when it kicks in. Most motorists don't notice stuff like this, but if you're paying attention you can hear it (especially When revving the engine while stopped with the window down). But since you haven't had any overheating issues, it's almost a certainty the fan is working correctly. Tim

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    Re: Fan / fluid coupling (fan clutch)

    For obvious reasons it can be dangerous testing these fans & clutches. So I'll start out with the obvious warnings: There are moving parts here and you can get hurt! Keep your hands away from the moving parts! Don't try this at home! If you disregard and do anyway, you do it at your own risk! Okay, nuff said. Here's how I test clutch fans. The 1st video is of poor quality but good enough to get the point across. In order to start it just click on the picture below:

    Click on the image below to view


    The video below is a little better quality & shows a working fan (testing this way takes a little longer). Sorry about bumbling around.......I get absent minded/distracted at times .


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    Re: Fan / fluid coupling (fan clutch)

    Excellent videos, Tim - thanks for those! I have a fan clutch or two needing to be rebuilt. Is there anything special to watch or adjust while rebuilding? How much silicone should be added? Should that o-ring around the inside perimeter of the clutch be replaced? I'd think that that's probably where the silicone leaks out. As always, thank you all in advance for your advice.

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    Re: Fan / fluid coupling (fan clutch)

    IMHO these are not worth messing with. I have a Toyota part number for the silicone goo, but no information as to how much to put in there. If you have one that's malfunctioning I would consider it disposable and buy a new one. I believe you can still get these from Toyota for around $150 or you can purchase aftermarket for around $40. I'm running a cheap aftermarket one right now and it's performing well. Tim

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    Re: Fan / fluid coupling (fan clutch)

    I think this may be my next project (issue to be solved). My fuel economy dropped from 24 to 16 recently. I am running a bigger tire and have a low profile solar panel on the top but I think the TPS was also to blame. I replaced that, reset timing and am now getting 19mpg. I am extremely conservative in my driving habits and I fully expect to get back up above 20mpg on the highway. My 22-re pulling a 4wd king cab with canopy would get 24 highway / 26 on good stretches.

    Am I unrealistic in my hopes for the 4yE fuel economy?

    Thanks for the video and testing scenario Tim. They are very helpful. Oddly I have been fighting an overheating issue too.

    I do have one remaining question for anyone....
    When I installed the TPS, why are the screw holes slotted? Was I supposed to calibrate or adjust this somehow in relation to the stop screw on the other side? I don't recall the shop manual addressing this at all.

    Thank you.
    Chris

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    Re: Fan / fluid coupling (fan clutch)

    Thanks for the kudos . For the TPS to function correctly it must be correctly adjusted. For all intensive purposes a new (but out of adjustment) TPS is no better than a failed TPS. There's a video link at the end of my 1st post in THIS THREAD that shows how to set it up. If you just want to check it without removing the throttle body, I show how to do that HERE. Good luck & have fun .

    BTW, it's much easier pulling the throttle body back off after a recent service. Based on your mileage improvement, it sounds like you may have accidentally got close to the sweet spot, but I'd still want to take it off and recheck. If you really don't want to do that, you could check the ECU for codes. If the TPS code hasn't come back, then you might be okay (your call). Tim

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    Re: Fan / fluid coupling (fan clutch)

    Update on aftermarket fan clutches. My TRW clutch I purchased at Napa made it almost 15k miles before it lost all it's silicone and quit working. Next I purchased a Hayden unit off of Rockauto.com and that one only lasted 5k miles. It was leaking almost from the beginning and finally quit engaging last week. I just purchased an Aisin (OEM) pump off Rockauto and will be putting it on tomorrow. It cost around $75 but I expect it to last for a long time. Tim

    Check out the label on the box. It even has the part number that Toyota calls out for this application #16210-73010.





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    Re: Fan / fluid coupling (fan clutch)

    That looks exactly like the OEM one I installed a few months ago. It's the one on the right in this picture:Name:  fanclutch.jpg
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    Re: Fan / fluid coupling (fan clutch)

    Is the fan clutch the same for 2wd and 4wd vans? I've had a bunch of worked preformed on my 4x4 van and I know Tim had mention to keep a healthy and cool running system. I haven't replaced the fan clutch but wanted to order one up so when it's time to replace it it'll be on hand.

    Thank you😊

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    Re: Fan / fluid coupling (fan clutch)

    At one point I think there were 2 or 3 different OEM part numbers for these. All would mount the same (interchangeable) so not sure what the difference was (suspect the 4wd ones were a bit more heavy duty?). I haven't checked lately, but I would assume they all cross over to the same part number now. Even if they didn't, I'd still get this one off rockauto than pay double for the one that comes in a Toyota box (I'd consider this Aisin to be every bit as good as one from Toyota.......probably the exact same thing). Tim

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    Re: Fan / fluid coupling (fan clutch)

    I have to say- everyone has their opinions about things like non-OEM thermostats, non-OEM gaskets, etc., but the fan clutch is one thing where I think it's easy to see the difference in quality. When I first got my van, the OEM fan clutch was toast and I just needed something that would let me diagnose other parts of the van. Bought one from AutoZone and it's currently on its way out; has about 20k on it. Will be either rebuilding my original OEM unit or purchasing a new Aisin brand.

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    Re: Fan / fluid coupling (fan clutch)

    Hey Tim, How's that Aisin 75$ aftermarket working since you posted? About to finally pull trigger on one...

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    Re: Fan / fluid coupling (fan clutch)

    It's been awesome so far (no leaks and it engages at appropriate times). The Hayden aftermarket clutch was leaking from day one. I can't believe what a fricken mess that thing made. Talk about the sh*t hitting the fan. Had just overhauled my engine, polished my manifold, painted, cleaned everything spotless, and only 5k miles later there was this nasty black mixture of silicone goo and road grime all over everything. And since the fan sits in the very front, it literally covered EVERYTHING. Of course this silicone stuff is not easy to clean off (nothing cuts it). The stuff that worked the best was silicone spray, so I used that. I finished that job about 2 or 3 k miles ago. I've been meaning to post, but have been putting it off.

    Here's some pics of the old one (if you consider 5k miles old) and the mess it made:









    Here's the new one ready to go back in:



    And here it is all snug in it's new home:


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    Re: Fan / fluid coupling (fan clutch)

    Thanks Tim for sharing. I'll be putting mine on a few days when it arrives. Everything on my cooling system has been upgraded or replaced except the clutch. I've been suspect about the thing. No overheating still, specially after I upgraded to a high efficiency radiator, but I've ran the tests you suggested and I'm gettin' mixed results. I'd like to drop that temp needle as far as I can..ha.

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    ..the Fan Clutch film....and a great radiator price,,,

    just watched your Youtube,,, https://www.youtube.com/watch?v=4sHCeyOrncA


    ....I was very surprised to see the fan clutch engage at half heat,,

    which brings up the question.... are the toyo temp gauges considered accurate?
    ....mine seem to usually engage the fan clutch at ~3/4 heat.



    ...and is there a way to test the clutches before installing?

    ,,,,I've recently gone through installing 2 different fan clutches,, both new,, both don't work!!

    ....would it work to heat the base in boiling water or on the heat element a few minutes?


    Found a great price for a 3row copper radiator...$220.... http://www.partsgeek.com/ss/?i=1&ssq...3530&x=21&y=10
    Last edited by micah202; 05-16-2016 at 11:45 AM.

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    Re: ..the Fan Clutch film....

    Did you read the previous posts in this thread?

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    Re: ..the Fan Clutch film....

    .

    ...sorry Tim,, I read the whole thread,, interesting, but didn't answer my related questions.....

    ....I was very surprised to see the fan clutch engage at half heat,,
    which brings up the question.... are the toyo temp gauges considered accurate?
    ....mine seem to usually engage the fan clutch at ~3/4 heat.



    ...and is there a way to test the clutches before installing?
    ,,,,I've recently gone through installing 2 different fan clutches,, both new,, both don't work!!
    ....would it work to heat the base in boiling water or on the heat element a few minutes?


    ​..it was good to see the difference between Hayden and Aisin in your review,, just in time to change my order!
    Last edited by micah202; 05-16-2016 at 12:00 PM.

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