Fan Clutch question HELP!!!!!!!!!!!!

red92stang · Jun 11, 2004

well i took most of my cooling system off (radiator, fan, shroud) and cleaned it up today. when i seperated the fan clutch from the fan it was caked with dirt and grime. the reason why i took everything apart was because i got up to 250*! I have a new t-stat with maybe 100 miles on it so it left me to believe that it was either my fan or the radiator. my waterpump still flows coolant so it cant be that.

My question is...are you supposed to be able to spin your fan after the engine has reached normal operating temp, let's say 190*? i heard you aren't supposed to be able to, bt i could spin mine all day i if i wanted. i noticed one or two teeth on the fan clutch were missing and some had rounded edges (dunno if that's how they're supposed to look). do i need a new fan clutch or are you supposed to be able to spin the fan?

red92stang · Jun 11, 2004

no one can answer this question?

Aryan15 · Jun 12, 2004

Fan clutch

I would replace the fan clutch because it sounds like it has been leeking and thats why they go bad. The fan should be hard to turn when hot and easy when cold. They are only like 60 bucks so it might be worth it. If the radiator is original, you should think about replacing that too. I have the exact same thing going on with my car right now. I need a fan clutch, fan, and radiator.

blk92stangg · Jun 12, 2004

Aryan15 said:
I would replace the fan clutch because it sounds like it has been leeking and thats why they go bad. The fan should be hard to turn when hot and easy when cold. They are only like 60 bucks so it might be worth it. If the radiator is original, you should think about replacing that too. I have the exact same thing going on with my car right now. I need a fan clutch, fan, and radiator.

I would agree on most of the above, except that a good working clutch should be hard to turn COLD, little easier when hot. Basically if the fan can turn more than a half revolution or so when cold, its shot.

HISSIN50 · Jun 12, 2004

Blk 92, i think you mis-typed. the clutch used on stangs is thermostatic. it should turn fairly easily when cold, and be HARDER to turn when warm. there are some tests to do, but they are somewhat subjective.

the dirt on the back of the clutch: that suggests the silicone in the clutch is leaking. anytime you see it leaking (often near the thermo-spring back there), replace it.

if it is original, i would get a new one. even new ones lose a few hundred RPM over the course of a year. once they start leaking, all bets are off.

good luck.

blk92stangg · Jun 12, 2004

Actually, no, not mistyped, although maybe my perception of "hard to turn" is different. My new clutch will not turn more than a half rev when cold, when it warms up it gets easier. The silicone in the clutch is sluggish when cold, when it warms up it becomes easier, so less hp drag. When it hits the right temp, I THINK it firms up a lot, thus allowing the fan to turn and cool off the car. When it cools off again then it becomes easier to turn again. I think its a misconception that it gets harder the warmer it gets. It will only get harder after a set point. Hissin, does your turn really easy when cold? Maybe you need a new clutch? Just wonderin' Of couse maybe I have a lousy clutch, and I am losing a bunch of HP to parasitic drag.

HISSIN50 · Jun 12, 2004

blk92stangg said:
Actually, no, not mistyped, although maybe my perception of "hard to turn" is different. My new clutch will not turn more than a half rev when cold, when it warms up it gets easier. The silicone in the clutch is sluggish when cold, when it warms up it becomes easier, so less hp drag. When it hits the right temp, I THINK it firms up a lot, thus allowing the fan to turn and cool off the car. When it cools off again then it becomes easier to turn again. I think its a misconception that it gets harder the warmer it gets. It will only get harder after a set point. Hissin, does your turn really easy when cold? Maybe you need a new clutch? Just wonderin' Of couse maybe I have a lousy clutch, and I am losing a bunch of HP to parasitic drag.

unfortunately, i think what you are describing is not possible. the resistance would look like a bell curve, if i read you right.
if the clutch is not getting harder to turn as the clutch heats up, the clutch is shot; its whole purpose is to do just that. i dont see how it could be variable AND reversable (when cold:easy. when warm: easier than cold, hot: hard). the resistance would look like a bell curve. i suppose this could be, if you live in a super-cold climate (i live 1/4 mile from the sun).

the fan clutch turns with resistance at all times on my car. when cold, it will spin a turn or two. when hot, about a half turn (using about the same amount of effort to turn it as before). like i said, this is where all of the subjectiveness comes into play.

my HD clutch has 600 miles on it. night and day difference between my old (OEM) one and this one.
the vary nature of a mech fan is that there will be parasitic loss, hence the reason many go to elec fans. it comes with the territory. the more loss, the better the fan should flow. im no expert, so this is just my two cents worth of thinking, Blk92.

now i have one for you, Michael, and the other smart folks in here: why cant they make an electromagnetic fan clutch (kind of like a/c compressors have). it would be thermostatic, and lock when the temps are right. while perhaps less efficient at mid-range cooling, it might be a nice idea..?

while the conventional set up is sorta like using a DCcontroller (like Michael uses), it is mechanical rather than electrical and prone to performance loss over time. my idea would be more like a conventional relay/switch set up with elec fans, but might be less prone to performance loss (either working or not working, like an a/c clutch). just a crazy idea....has anyone heard of such a thing (im sure it is a stupid idea, but im curious about it).

blk92stangg · Jun 12, 2004

I hear ya Hissin, I may be wrong, but this is what I thought was going on with the fan clutches:

I thought the regular silicone clutches just spun at a slower rate at higher speeds, using the shear from the silicone in the clutch. Low RPMS high drag, high rpms low drag (kinda like a flex fan, in fact). Thermostatic clutches, i thought, were the same as the silicone clutches, just that there was that coil thing on the back that locks iat high temps, regardless of engine speed.
So in essence, I guess it would look like a bell curve. When cold the silicone is more viscous, and the fan is harder to turn. As it heats up to operating temperature, it becomes a little easier to turn, but still only a half rev or so. When it hits the high point, it should be very difficult to turn due to the coil locking it down on the back. I think it depends what kind of clutch you have, but when it boils down to it, if the clutch is really easy to turn at any temperature, it is shot. When mine was gone, it would spin 2-3 revolutions.

Idwitheld-1` · Jun 12, 2004

HISSIN50 said:
unfortunately, i think what you are describing is not possible. the resistance would look like a bell curve, if i read you right.
if the clutch is not getting harder to turn as the clutch heats up, the clutch is shot; its whole purpose is to do just that. i dont see how it could be variable AND reversable (when cold:easy. when warm: easier than cold, hot: hard). the resistance would look like a bell curve. i suppose this could be, if you live in a super-cold climate (i live 1/4 mile from the sun).

the fan clutch turns with resistance at all times on my car. when cold, it will spin a turn or two. when hot, about a half turn (using about the same amount of effort to turn it as before). like i said, this is where all of the subjectiveness comes into play.

my HD clutch has 600 miles on it. night and day difference between my old (OEM) one and this one.
the vary nature of a mech fan is that there will be parasitic loss, hence the reason many go to elec fans. it comes with the territory. the more loss, the better the fan should flow. im no expert, so this is just my two cents worth of thinking, Blk92.

now i have one for you, Michael, and the other smart folks in here: why cant they make an electromagnetic fan clutch (kind of like a/c compressors have). it would be thermostatic, and lock when the temps are right. while perhaps less efficient at mid-range cooling, it might be a nice idea..?

while the conventional set up is sorta like using a DCcontroller (like Michael uses), it is mechanical rather than electrical and prone to performance loss over time. my idea would be more like a conventional relay/switch set up with elec fans, but might be less prone to performance loss (either working or not working, like an a/c clutch). just a crazy idea....has anyone heard of such a thing (im sure it is a stupid idea, but im curious about it).

To answer your question about electromagnetic clutch fans...
1. higher complexity
2. more parts, less modular integration

= higher cost.

Plus you would have the fan drag / parasitic losses AND electromotive parasitic losses from a clutch coil.

I see you recently moved farther away from the sun.

87'GTstang · Jun 12, 2004

Hissin is correct about the hot/cold situation. Let me see if I can describe it from another point so you can understand it better. The fan clutch IS thermostatic and the thing you must remember is that it is attatched to the pulley on the water pump which in turn is connected by the belt and all the other goodies on the belt system. Now, being that it is a clutch design means that it has the ability to enagge and disengage to an extent. The average clutch will have about 70% drag and obviously 100% at full lockup or when it gets to that certain temp. Now when it gets hot and it does lockup 100%, in keeping with the theory in which all the other things the fan is directly connected to, the clutch kind of has "full grabbing" effect on the fan. Therefore when it's hot, and the clutch has locked up to control cooling and in turn allows the fan to spin faster, you have less rpm seperation between the fan itself and the clutch. There other part with the belt system is remember that it takes a certain amount of force to turn all of these other pulleys and their respective devices (crank included). So in the end it will be harder to turn the fan because of this full lockup stage and what is happening is the fan itself has more of a stronghold on the belt system intself because of the clutch being locked at 100% instead of the less-drag at 70%.

Yeah I guess it's hard to explain, but it does go with the whole concept of drag in mind.

Fan Clutch question HELP!!!!!!!!!!!!

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