fan clutch
09-28-03, 01:20 PM
#1
fan clutch
Where is the fan clutch I think mine is bad because I can actually stop the fan with my hands. THere is a parts car around here that a guy doesn't mind me taking stuff from I believe its an 87 se is the fan clutch the same on that car? Please any help would be great! I would like to keep the stock fan because I can use the fan shroud to place my msd6a on it. Thanks
09-28-03, 01:48 PM
#2
What year FC do you have? If It's b'n 86-88 than you will be alright. Check here for pics/prices If that doesn't go through. http://www.mazdatrix.com/b9.htm
09-29-03, 08:27 AM
#7
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Fan clutch basics:
The fan clutch uses a silicon oil viscous fluid in two chambers inside.
The Bi-metal strip on the front bends outward as it warms and opens the valve from the reservoir side to the clutch side.
Centripetal force provides the pumping action to move the fluid.
After 100,000 miles the bearing seals wear, and the bearing lube weakens the clutch fluid's grip.
Both the S4 & S5 clutch freewheel when cold.
The s4 clutch increases it's bite gradually with temperature rise.
The s5 clutch is more on-off. (It just coasts until is gets warm)
Once they are warm, the fan speed goes up with engine speed to about 4000 RPM.
As the engine revs higher the fan stays at ~4K.
If your warmed up fan only revs up to ~2500 RPM, it's bad.
The fan clutch uses a silicon oil viscous fluid in two chambers inside.
The Bi-metal strip on the front bends outward as it warms and opens the valve from the reservoir side to the clutch side.
Centripetal force provides the pumping action to move the fluid.
After 100,000 miles the bearing seals wear, and the bearing lube weakens the clutch fluid's grip.
Both the S4 & S5 clutch freewheel when cold.
The s4 clutch increases it's bite gradually with temperature rise.
The s5 clutch is more on-off. (It just coasts until is gets warm)
Once they are warm, the fan speed goes up with engine speed to about 4000 RPM.
As the engine revs higher the fan stays at ~4K.
If your warmed up fan only revs up to ~2500 RPM, it's bad.
Last edited by SureShot; 09-29-03 at 08:31 AM.
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09-29-03, 08:34 AM
#8
thanks for the history on the fan clutch I really didn't know how the fan clutch worked at all, all I knew was that I can actually stop the fan when the car is running. I took the fan out yesterday because I found a shroud that looked beter than mine off a parts car. however when I took it off I could actually spin the fan with my hand. Like jpa said if I can spin it with my hand is it bad? Thanks
09-29-03, 08:39 AM
#9
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Looks like I was wrong, as Sureshot says they freewheel when cold. I know that mine was slipping and pinning it (making it go all the time) helped immensly, and was free. Of course it is now louder, but I don't care... drowns out the loose exhaust LOL
09-29-03, 11:23 AM
#11
Engine, Not Motor
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The term "freewheeling" is open to interpretation. If the clutch spins eaily with no resistance, then it's dead. Even cold, there should always be some resistance. It should spin about half a turn when given a good spin.
09-30-03, 03:17 PM
#13
Engine, Not Motor
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Originally posted by RoninAutoBoX
Oh.....so your fan can't even slip to avoid power loss! That's not a good thing. Have a solid hub fan will cost you considerable power!
Oh.....so your fan can't even slip to avoid power loss! That's not a good thing. Have a solid hub fan will cost you considerable power!
It does not slip to avoid power loss. It slips to avoid cooling when cooling is not necessary.
09-30-03, 04:34 PM
#14
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I understand that, but a solid hub fan does not slip, and that lack of slippage costs a great deal of power. On the old school cars, switching from a solid hub design to a viscous design will easily net over 10hp alone. On larger engined vehicles, this can be as high as 20 hp.
I know it slips to avoid cooling, but that slippage also prevents the engine from have to immediately match the fan's speed to the engine's speed.
I know it slips to avoid cooling, but that slippage also prevents the engine from have to immediately match the fan's speed to the engine's speed.
09-30-03, 07:33 PM
#16
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Man, torch that old clutch fan and install an electric, the power gains from getting rid of the drag on the motor is well worth it, besides that, you can dial in the start temp to keep the engine cooler. I ran one all summer this year and wouldn't go back to the other for anything
09-30-03, 08:52 PM
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The stock S4 fan clutch drags some even when cold.
The S5 clutch, and some aftermarket S4 clutches spin much easier when cold.
The test is - after the clutch bi-metal is fully warm - does the fan speed go up directly with engine speed to ~4k?
On a worn S4 clutch, you can bend the bi-metal outward to get a little more bite.
The S5 clutch, and some aftermarket S4 clutches spin much easier when cold.
The test is - after the clutch bi-metal is fully warm - does the fan speed go up directly with engine speed to ~4k?
On a worn S4 clutch, you can bend the bi-metal outward to get a little more bite.
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