Fan Clutch Question

[dannyvp]

Driving my truck yesterday after a top end rebuild, the truck ran really cool. 1/4 up the temp gauge. (the hood is off so lots of air flow)
When i stopped at a red light the temp climbed to 1/3 temp gauge, then back to 1/4 when i started driving. When i parked in my garage, the temp climbed to little over 1/3. So my question..... Is my fan clutch working properly?

While the truck is idling the clutch does not engage. If i increase the RPM's the fan clutch engages.

 

[OSS]

That's normal.
If you drive it for a while so everything is hot (highway etc) and then stop & go into a store to get something, when you come back and turn the key to ON, the temp gauge needle will be near the top. That's normal too.

 

[dannyvp]

That's normal

I was thinking that when the clutch is warm it was suppose to engage even if its only idling.

 

[OSS]

It depends.
It can free spin when at idle right after driving because the fluid has spun out to the secondary chamber. The fan is supposed to free spin at driving speeds if the air flowing out through the radiator isn't too hot.

If the radiator (and therefore the air flowing through the radiator) gets hot enough, the temp sensor valve at the front of the clutch will rotate and change the way the fluid flows inside the clutch - locking it up so the fan will spin.

Regardless of how hot or cold the radiator is, when the engine is started after sitting for a few minutes, the clutch will lock up because the fluid has migrated back to the clutch chamber because of gravity

 

[dannyvp]

It depends.
It can free spin when at idle right after driving because the fluid has spun out to the secondary chamber. The fan is supposed to free spin at driving speeds if the air flowing out through the radiator isn't too hot.

If the radiator (and therefore the air flowing through the radiator) gets hot enough, the temp sensor valve at the front of the clutch will rotate and change the way the fluid flows inside the clutch - locking it up so the fan will spin.

Regardless of how hot or cold the radiator is, when the engine is started after sitting for a few minutes, the clutch will lock up because the fluid has migrated back to the clutch chamber because of gravity

So i never get the "roar" of the fan being engaged unless i am manipulating the RPM's.

 

[BlackCat]

So i never get the "roar" of the fan being engaged unless i am manipulating the RPM's.

Same as everyone else. Your locked fan clutch isn’t going to roar at 700RPM at idle. It’s going to roar at 2,000+ when it’s pulling all the air.

 

[OSS]

It won't roar at idle. Only noticeably at about 1500 rpm & up when locked. If the fan clutch is over about 12-15 years old, a new one might perform a little better. My "old" fan clutch was about 20 years old and seemed to work normally- it would engage when hot- but I swapped it anyway, and the new one performed differently, it would lock up stronger and earlier- it worked noticeably better.
My old FC didn't have a leak or anything, just the fluid viscosity broke down with age.

 

[dannyvp]

Ok i was assuming when traveling at speed you didn't need as much Fan Clutch Speed bc your air flow was coming from truck movement and that when sitting at the red light is when you needed air from the Fan Clutch bc your not moving.

 

[BlackCat]

Ok i was assuming when traveling at speed you didn't need as much Fan Clutch Speed bc your air flow was coming from truck movement and that when sitting at the red light is when you needed air from the Fan Clutch bc your not moving.

You’re missing the main point. Have you ever put a box fan in one of your windows at home on a nice day? Speed one is fairly quiet, right? That’s idle in your land cruiser. Speed 3 is real noisy on the box fan, right? That’s a locked fan clutch at 3k RPM.

 

[dannyvp]

You’re missing the main point. Have you ever put a box fan in one of your windows at home on a nice day? Speed one is fairly quiet, right? That’s idle in your land cruiser. Speed 3 is real noisy on the box fan, right? That’s a locked fan clutch at 3k RPM.

I was assuming that it should be different. Speed 3 when sitting still bc you need more air flow, speed 1 while moving bc the truck movement was helping create airflow.

 

[BlackCat]

I was assuming that it should be different. Speed 3 when sitting still bc you need more air flow, speed 1 while moving bc the truck movement was helping create airflow.

A motor at idle isn’t generating nearly the same heat as it is at 3,000RPM.

 

[Skniper]

I was assuming that it should be different. Speed 3 when sitting still bc you need more air flow, speed 1 while moving bc the truck movement was helping create airflow.

Doesn’t depend on speed, depends on how hot the air is after it passes through the radiator. The fan can engage at any speed and at idle, you just don’t tend to hear it much at low speed. The fan is always pulling air but it’s pretty “passive” until the clutch locks, then it pulls air aggressively the same speed as the motor is turning, at 2000+ rpm it’s the “roar”....or 3 on the home fan.

It’s also why a complete fan shroud is so important, to funnel/concentrate air through the radiator to the fan clutch.

 

[dannyvp]

I’ve watched the truck idle for 30 minutes. The temp will be a 1/3 up the gauge. And the fan clutch will only engage of you change the RPM.
While test driving as soon as you get off the gas, the fan clutch disengages.

 

[Gretsch]

While test driving as soon as you get off the gas, the fan clutch disengages.

How are you determining its disengaging? By sound?

 

[dannyvp]

How are you determining its disengaging? By sound?

yes.
My hood is off right now, so I can hear and feel it when it’s engaged.

 

[Gretsch]

Same as everyone else. Your locked fan clutch isn’t going to roar at 700RPM at idle. It’s going to roar at 2,000+ when it’s pulling all the air.

I was assuming that it should be different. Speed 3 when sitting still bc you need more air flow, speed 1 while moving bc the truck movement was helping create airflow.

I don't think clutch would be disengaging at lower RPMs. More likely it is just not producing the same amount of air at idle it does at higher RPMs which could sound like its disengaging. If the clutch locks up enough to produce air flow at higher RPMs, then its working. I don't really know how you would determine its locking up at 2400 but not at 600. Its either locked or its not and if its locked, it would really only produce significant audible airflow/sound at higher RPMs. If there is a question about the clutch operation then you should prolly just replace it. Made a world of difference in my truck as far as cooling. HTH.

 

[dannyvp]

New clutch came in today. Look at the difference!

When I tested my engine, everything seemed to be working, when I shut it off, I noticed the fan was still spinning, that’s a first for me to see.

 

[dannyvp]

I just went back and checked it and the clutch tightened back up and now has force against it.

 

[Spike Strip]

That's not the way to check a fan clutch, by just spinning it when motor stopped.

It 'locks up' when ambient temp is high to pull air in, past radiator fins. To test, when hot, and engine on, try and try and slow the fan with a rolled up newspaper. Good clutch should not slip when ambient temp is hot. Will slip when cooler so less drag on engine when air is being forced by radiator when vehicle is moving.

 

[Elbert]

any high milage or decades old vehicle, I would automatically replace the fan clutch. If there was a source for OEM or other good quality replacement part. In general a fan clutch responds to heat. In high ambient temps and the engine fully warm....you'll hear the fan clutch or the sound of the fan as it pulls air across the radiator where the engine is accelerating around 2K rpm or so (the roaring noise) Once fully warm and reasonably high ambient temps, when the engine shuts off the radiator fan should have some resistance to free spinning when turned by hand. When the engine is stone cold the radiator fan should spin reasonably well with little to no resistance when turned by hand (engine off).

There are a lot of variables in the mix, but when the engine is fully warn you should generally hear the fan clutch engage pending how hot it is outside and how hot the air is coming across the radiator. Often times in the winter you will not hear the fan clutch engage too often.

Give the price of a good fan clutch and the relative ease to swap.....just get a new one.

Problems I've observed with fan clutches (1) they may lock up all the time...this is likely the lesser of the failure points, you'll hear extended roaring noise or roaring noise all the time. (2) the truck runs hotter or hot for no obvious reason (generally in the summer and at lower vehicle speed, in-town driving and you notice that you don't hear the fan clutch engage (the roaring noise). Put a new fan clutch on.

I always buy OEM fan clutch if possible or DENSO, if other brand of mfg (other than toyota) I by the OEM, no aftermarket fan clutch stuff unless there is no other option. Had good service out of a beck arnley fan clutch on a 60 one time because that was all I could get the next day.