Stuck Fan Clutch even after replacement?

Hi guys, I'm a new member here but I've found a lot of helpful answers here in the past.

But now I've got an issue with the family Tacoma ('95 2.7L 4x4) and even my dad who was a mechanic hasn't any idea of what could be causing it. And researching the problem doesn't turn up anything useful.

The fan clutch recently became stuck; it was always running and never seemed to disengage.
The obvious course of action was to replace it and so we did--except that hasn't fixed it.
At first it seemed like maybe we got a bad aftermarket part, but after taking a working fan from the other truck and comparing, that doesn't appear to be the case.

So, does anyone know what else could be causing it to stay engaged all the time?

Thanks in advance. Also, I hope I'm posting this in the right place.

 

This doesn't seem possible unless the part is bad. Its a mechanical clutch, did you also swap the fan blade form the known working part? The part you swapped was also from a similar 2.7 Tacoma?

 

How do you know that its engaged all the time? Will it spin with the engine off?

 

it is supposed to be tight and just be able to turn with resistance, it doesn't free spin as others do.

if you think its engaged just because its stiff to turn then that is its normal condition

 

That's what i was getting at. It will also spin with the engine on regardless if its bad or not. I just replaced mine last night and the clutch that crapped out felt almost the same amount of resistance compared to the new one on the workbench, yet once the new clutch was installed and the engine running you could feel it moving more air and you could hear it engage and watch the temp gauge drop on my test drive. The way i found out mine was bad was my truck kept overheating while off-road with the AC on and even getting real hot in traffic and it never used to do that. I had a friend who is a mechanic look at the fan while stopped on the trail and the temp gauge pegged, and the fan spun freely. He said the fan clutch was bad because it should not spin when hot and be locked up.

 

I think there is confusion on what this is supposed to do. It's supposed to spin slower that the engine RPM, at a fairly constant speed, regardless of RPM. If it fails, it will lock up completely and spin at the same rate as the engine, usually causing the fan blade to shatter.

 

And will be loud. Just like it sounds when you first start the truck. Just loud all the time.

When mine went bad and I changed it, I got 2 mpg better.

 

That's how a non thermal fan clutch works Caligula. We have thermal fan clutches, they operate based of engine temperature and "lock up" when the thermal spring expands and unlocks once it cools down.

http://www.haydenauto.com/upload/HaydenAuto/Documents/Cat_Hayden/Fan_Clutches_How_They_Work.pdf

Link that breaks down how they work and how to trouble shoot it: http://www.haydenauto.com/Fan Clutch Tutorial-Part 1/Content.aspx

Mine failed in the unlocked position. It would never lock up and made a god awful grinding noise which i always assumed was a pulley bearing waiting to die.

 

Some more poop on the hydraulic Aisin clutch and how to tweek the lock up point.

 

so what is your opinion? do you think a fan clutch should be replaced due to its age or mileage like a timing belt, or just wait until you have some reason to think its bad?

I don't think I have the balls to be messing with adjusting it or tweaking oil levels but I would change it if I thought it needed it or if its a good idea based on truck miles

 

Replace it when it craps out. Or you can just do what one of my wheeling buddies did and just drill a self tapping wood screw through it and call it good lol!!

 

no I don't do stuff like that, but I used to in my younger and more foolish "I don't care long what it looks like as long as it works" days lol