Ok, I need your tests guys.

I need you to go out to your trucks when it is dead cold and try to spin the fan and tell me:

Does it spin freely?
Does it not spin?

Also, allow you truck to warm up to operating temperature and then allow it to sit and idle for 10 minutes to get it good and hot. Best to also turn your AC on max to heat the AC system up. After 10 minutes, tun the truck off completely and remove the keys.

Does the fan spin relatively freely?
Does it not spin and is really stiff?

Everyone pitch in here so everyone can learn.

I am counting on your guys.

okay, I'll bite ...


truck is about 3 1/2 hours cold ...

fan spins rather easily however, it doesn't feel loose either ...

if it helps at all, it feels "normal" ...

... gotta wait till morning for the totally cold test ...




Ok, I need your tests guys.

I need you to go out to your trucks when it is dead cold and try to spin the fan and tell me:

Does it spin freely?
Does it not spin?

Also, allow you truck to warm up to operating temperature and then allow it to sit and idle for 10 minutes to get it good and hot. Best to also turn your AC on max to heat the AC system up. After 10 minutes, tun the truck off completely and remove the keys.

Does the fan spin relatively freely?
Does it not spin and is really stiff?

Everyone pitch in here so everyone can learn.

I am counting on your guys.

Yea, mine feels the same way.

I don't know when the stock fan clutch lock up though.

I sat with my truck idling with the AC on max for 15 minutes to try to get it heated up to see if the clutch got tighter and it did but not by much.

Everyone, go out and spin your fan whether cold or hot and let us know.

Mine spins pretty freely though not completely free though when cold. I'll post back when I get a chance to check it warm. I do get that nice loud disel wooooosh when I start it up though. I decided to use this opp to go electric. Same price and if I don't like it I'll through a clutch fan back on.

I'd like to see if it spins relatively freely when the engine is hot and up to temperature at idling for 5-10 minutes.

well i just got home from a 30 mins ride and engine is plenty warm. spun the fan with just as much ease as i did it when it was cold..

I'll check mine when my gf gets home. Ever had one sieze up on you? I had it happen on my 88 and it sounded like my engine was in a wind tunel. A great loss of power too. Couldn't turn the fan for nothing.

It's real hard to tell the difference between hot and cold. But I noticed when my truck is cold the fan is loud for about 30 sec then quiets down.
I changed it last year because every time i went slow or came to a stop the temp would climb. Put in a replacement one loud all the time put in another one loud all the time. Put in the exact oem never had another problem.

for what it's worth ...

The Haynes for my 97 says that the fan clutch should engage between 150-195 degrees ...

today, i didn't notice much difference in the feel of the rotation of the fan when engine was hot or cold ...




Yea, mine feels the same way.

I don't know when the stock fan clutch lock up though.

I sat with my truck idling with the AC on max for 15 minutes to try to get it heated up to see if the clutch got tighter and it did but not by much.

Everyone, go out and spin your fan whether cold or hot and let us know.

This is what I am feeling as well and seeing the air temperature might not be getting that high, it might not be completely locking up which is normal.

Looks like we all are good though, you won't see this kind of testing continuity anywhere.

Everyone still chime in!

do you have the "test" written in your year repair manual ?

mine says "tape a thermometer to the inside of the shroud ... cover the grille in front of the vehicle with cardboard to block the airflow temporarily. Have assistant run the engine to temp ... note the temp when the clutch engages ...

u using a cooler thermostat? would that affect engine compartment temp? I've never used a cooler stat so Im not sure

LT, check my logic here ...

The fan clutch operation is regulated by a valve that is opened and closed by a thermostatic spring. The valve controls the flow of a viscous silicone fluid between chambers in the clutch assembly. When the engine is cold, the clutch is essentially disengaged, which is why the fan runs at its slowest compared to the engine's speed. As the engine warms up, the air flowing to the fan assembly becomes hotter. The hotter air causes the thermostatic spring to unwind and open the valve. Silicone fluid from the reservoir chamber flows into the main chamber, engaging the clutch, and the fan spins faster ...

so ... when you turn off the engine to feel whether or not the fan feels loose, the feel will be the same whether hot or cold. It is the centrifugal force of the fluid in the main chamber that "grabs" the engine rotation - not so much the fluid pressure or a drag from viscosity ... of course when the engine isn't rotating, there is no centrifugal force

i don't think it "locks" ... I think even at its warmest, its slightly slower than engine rotation ...





This is what I am feeling as well and seeing the air temperature might not be getting that high, it might not be completely locking up which is normal.

Looks like we all are good though, you won't see this kind of testing continuity anywhere.

Everyone still chime in!

Read where it states how to test it in the repair manual and online.

It is not centrifically controlled, it is temperature controlled.

Our blazers must not be getting hot enough to have them go full speed then.

yes and no

the spring is thermostatically controlled but it is the centrifugal force of the fluid that causes it to engage, is it not?

... the temp affects the spring ... just like a thermostat ...

you say " our blazers must not be getting hot enough to have them go full speed ..." how are you assessing what is "full speed"?

are you saying the engine compartment never reaches 150-195 degrees ?




Read where it states how to test it in the repair manual and online.

It is not centrifically controlled, it is temperature controlled.

Our blazers must not be getting hot enough to have them go full speed then.

yes and no

the spring is thermostatically controlled but it is the centrifugal force of the fluid that causes it to engage, is it not?

... the temp affects the spring ... just like a thermostat ...

you say " our blazers must not be getting hot enough to have them go full speed ..." how are you assessing what is "full speed"?

are you saying the engine compartment never reaches 150-195 degrees ?

No, because if it was, when we revved our engines the fan would lock on which would not be a good thing.

The fan clutch is thermally controlled only.

I havn't had time to try your test yet but it seems mine kicks in at about 220. I have had it kick on at red lights a few times on REALLY hot summer days.

Some insight here:

http://yarchive.net/car/fan_clutch.html

Pay attention the the fellow by the name of jgd@mathcs.emory.edu (John De Armond) (Scrolling about mid-way down, and the article follwing that. It's interesting and makes sense...

The fan speed is controled by the viscous fluid in the clutch, it doesn't ever really "lock in". The operation of the clutch is very similar to how a torque convertor in a tranny works.

yes, and torque converters use the centrifugal force of the fluid as I said before ...

isn't this also true for in a similar sense for visc fl clutches too (along with a thermostatic spring and, to some degree, the fluid expanding from heat)





The fan speed is controled by the viscous fluid in the clutch, it doesn't ever really "lock in". The operation of the clutch is very similar to how a torque convertor in a tranny works.

no, the fan clutch is NOT centrifugally controlled, it is TEMPERATURE controlled by the fluid properties inside the clutch.

If ou are saying it is centrifugal, when ever you revved you engine the fan clutch would enagge more which is wrong.

no ... the centrifugal force is what causes the fluid to shear at higher rpms (when you rev the engine). This is what causes the clutch to slip at higher rpms. the slipping is necessary and desirable for optimum engine load. this is why our "early morning roar" goes away after a few seconds and a good rev ...

agreed, yes, the fan is temperature controlled ... actually, ACTIVATED is a better term. agreed it is the fluid properties at work inside the clutch that controls aspects of the fan. centrifugal force is still at work though in that the fluid shears (fluid property) as it rotates faster. this, along with cooling fluid, is what allows the clutch to slip at higher engine rpms. conversely, the expanding properties of the fluid and less centrifugal force allow the fan to grab at lower rpms (when the engine needs the fan's cool air the most).




no, the fan clutch is NOT centrifugally controlled, it is TEMPERATURE controlled by the fluid properties inside the clutch.

If ou are saying it is centrifugal, when ever you revved you engine the fan clutch would enagge more which is wrong.

interesting cutting-edge stuff ...


http://www.gm.com/company/careers/career_paths/rnd/prj_magnetorheological.html





The fan speed is controled by the viscous fluid in the clutch, it doesn't ever really "lock in". The operation of the clutch is very similar to how a torque convertor in a tranny works.

Back on topic, anyone else tested their fan for me when cold and warm?

Need everyone's testing done.

Alrighty BLT , I spun the fan (Dead cold), it spins but is a little snug. Took the truck out for a 50 min drive, shut her down and spun the hot fan again and it still feels snug, I can't really tell a big difference cold or hot ? ? ?

:smokin: WTF...

dude, if it as snug it wouldn't be turning.

What you are saying is that is still turned relatively freely when hot or cold.

Alrighty BLT , I spun the fan (Dead cold), it spins but is a little snug. Took the truck out for a 50 min drive, shut her down and spun the hot fan again and it still feels snug, I can't really tell a big difference cold or hot ? ? ?

:smokin: WTF...

That is to be expected. The motion of the input shaft is transfered to the fan through the fluid. It transfers the motion well at engine speeds, but the 10 - 20 RPMs that you can turn it by hand isn't fast enough to generate enough resistance to tell a difference by hand, even if the motor is at a temp were the fan would be engaged if it were running.

yes. it's not just the fluid at work, rpms and resistance are a factor

only if the fan clutch is failing would you get differences by hand - more than likely either frozen or free-wheeling ...



That is to be expected. The motion of the input shaft is transfered to the fan through the fluid. It transfers the motion well at engine speeds, but the 10 - 20 RPMs that you can turn it by hand isn't fast enough to generate enough resistance to tell a difference by hand, even if the motor is at a temp were the fan would be engaged if it were running.

What you are saying is that is still turned relatively freely when hot or cold.


Yes, turned relatively free With a little tiny bit of "Resistance" (Better word then snug)
Hot and cold...

ah, ok, mine is the same too.

Cool beans.

Fan is loud for about 15 seconds on a cold start then quiets down.
Seems to have about the same drag with engine hot or cold.

what are we doing here ???????? what are we "testing" ??????? everybody's results are the same and the reason has been explained ...

blazee ... where u at ????????

hey everybody ... go test your tires for me !!!! if they're round and spinning, report back !!

BLT ... why so vague ??????????????? what point are you looking to make thru the results of the replies ??!! just say it !!

uggghhhhh .............




Fan is loud for about 15 seconds on a cold start then quiets down.
Seems to have about the same drag with engine hot or cold.

what are we doing here ???????? what are we "testing" ??????? everybody's results are the same and the reason has been explained ...

blazee ... where u at ????????

hey everybody ... go test your tires for me !!!! if they're round and spinning, report back !!

BLT ... why so vague ??????????????? what point are you looking to make thru the results of the replies ??!! just say it !!

uggghhhhh .............

Simmer the hell down there......

The obvious point of this thread was to see if my clutch was normal or not.

okay, gotcha ... will simma' down' na ...

... admittedly, I was a little confused ... ... ... you never said that you were asking for feedback concerning whether or not YOUR clutch was normal ...

nor did you describe any abnormalities in your own clutch ...


.. still not sure (without mechanical failure) how spinning the fan clutch (with knowledge of how it works) by hand (with engine cold and/or hot) is beneficial to the patrons of this forum ...







Simmer the hell down there......

The obvious point of this thread was to see if my clutch was normal or not.

okay, gotcha ... will simma' down' na ...

... admittedly, I was a little confused ... ... ... you never said that you were asking for feedback concerning whether or not YOUR clutch was normal ...

nor did you describe any abnormalities in your own clutch ...


.. still not sure (without mechanical failure) how spinning the fan clutch (with knowledge of how it works) by hand (with engine cold and/or hot) is beneficial to the patrons of this forum ...

Since when do I have to only post threads that have a use for everyone? I don't see that in the rules here.

I was asking people about how their fans were working hot or cold and whether or not the way my fan was working was normal.

I asked, they responded and I really appreciate it.

Whether you understand the point of this thread I really don't care about, it was to serve my purposes and to see what is the normal operating consitionof these fans are.

But thanks for caring so much.

Since when do I have to only post threads that have a use for everyone? I don't see that in the rules here.

Agreed, I never said that you have to only post threads that have a use for everyone, nor did I comment on any blatant or implied rules that are in effect for patrons ...




I was asking people about how their fans were working hot or cold and whether or not the way my fan was working was normal.

yes I know you were, and as I said ...

.. still not sure (without mechanical failure) how spinning the fan clutch (with knowledge of how it works) by hand (with engine cold and/or hot) is beneficial (rule or not) to the patrons of this forum ...




I asked, they responded and I really appreciate it.

Whether you understand the point of this thread I really don't care about, it was to serve my purposes and to see what is the normal operating consitionof these fans are.

... the normal operating conditions have been explained ...




But thanks for caring so much.



Since when do I have to only post threads that have a use for everyone? I don't see that in the rules here.

I was asking people about how their fans were working hot or cold and whether or not the way my fan was working was normal.

I asked, they responded and I really appreciate it.

Whether you understand the point of this thread I really don't care about, it was to serve my purposes and to see what is the normal operating consitionof these fans are.

But thanks for caring so much.

lol, seriously, let it go would ya, I tested my fan, did the research and I thought that my clutch was defective.

I started this thread to find out if my fan was like every other....and that is it.

Please, stop questioning my intentions because even a chimp can see the meaning behind this thread.

I was not wanting to find out how they work, I was seeing if everyone else's fan worked like mine.

I'm a little late for the "test" but would like to share my problem with the experts and hopefully get a solution.

I noticed this summer (outside temps range from 95 to 101 with 100% humidity for 3 to 4 months out of the year) when my Blazer was at a complete stop, the temp gauge went a quarter past 210 (I guess it hit 225 to 230). But as soon as I began to drive, the fan got loud and the temperature slowly went to normal (a tick or two before 210). Once the temp gauge went to normal, the fan noise went back to normal as well.

I only noticed it twice this summer since the blazer is mainly driven by my wife.

She doesn't notice anything so there is no telling how many other times it has occured.

I performed the test stated in the Haynes manual while dead cold and after it sat for about 3 hours in the garage at night.

Here are the results:
DEAD COLD - Turned it and got firm resistance and the fan moved maybe a quarter of a revolution but after 5 or 6 times of testing, it started to free-wheel and go beyond a full revolution.

WARM - Turned it and got firm resistance after 5 or 6 times. Never free-wheeled after that.

I would suspect the clutch fan but not sure if this is normal or not. I didn't read where this happened to anyone else during LT's testing of a cold engine.

In addition, my dad suggested replacing the clutch fan with a flex fan. Not sure if this is a good idea since it would be running/cooling all the time. I would suspect it would put more stress on other parts (ie water pump).

A suggestion by Flex-a-lite was to remove the clutch fan and replace it with 4 electric fans, 2 on the outside of the rad (pushers) and 2 on the inside (pullers). Suppose to free up horsepower and take the stress off the water pump. The problem with this type of cooling is the fans are around $80/each plus misc electrical components.

Thanks.

no ... the centrifugal force is what causes the fluid to shear at higher rpms (when you rev the engine). This is what causes the clutch to slip at higher rpms. the slipping is necessary and desirable for optimum engine load. this is why our "early morning roar" goes away after a few seconds and a good rev ...

agreed, yes, the fan is temperature controlled ... actually, ACTIVATED is a better term. agreed it is the fluid properties at work inside the clutch that controls aspects of the fan. centrifugal force is still at work though in that the fluid shears (fluid property) as it rotates faster. this, along with cooling fluid, is what allows the clutch to slip at higher engine rpms. conversely, the expanding properties of the fluid and less centrifugal force allow the fan to grab at lower rpms (when the engine needs the fan's cool air the most).

This is exactly how it works. It should be about the same even when the engine is warm, it should not free wheel. To check to see if your clutch is working, when the engine is warm, pop the hood and let it idle. After a few seconds 10 -15 seconds approx, the fan should begin to engage, you'll feel the difference of air volume when it begins to engage. If it engages and dis engages, or, never engages, its just about time for a new clutch. You'll know when it engages, you'll feel the difference of air if your over the engine.

The best way to check it is to feel the air it is blowing out towards the engine.
Also if you have good ears you can hear it kick in full force.
When it reaches the preset tempt you can feel it kick in and start blowing air full force.
Just feeling the fan rotation does not tell you much.
When it starts blowing air full force it is kicked in.
MT-2500

another late entry...

Checked mine totally cold & it doesn't free spin at all. I can move it with my hand, but as soon as my hand comes off, it stops moving.

Drove it about 12 miles (avg about 50 mph) then back to the garage to do the test from the Haynes manual where you let it run ~10 minutes with the radiator covered. After all that, I tried to spin the fan again.
At this point it will keep going about 1/4 turn after I take my hand off.

Sound normal, or no?

My Blazer still runs cool, I think. Never goes more than one tick past the 1/4 mark on the temp gauge. Already checked the gauge itself, replaced the temp sending unit & replaced the stat with a 195 deg Stant.

-Mike

My dumb butt actually held on to a fan while a friend? started the motor so I could get it to warm up faster after a water pump replacement(96 s-blazer vortecV6). Drag slowly increased as temprature went up. I felt uncomfortable holding it somewhere between 160-180.
dont try this at home kids for I am just a dumb hillbilly

Resistance while cold. But not so much after hot.