Fan Fluid Coupling (1 Viewer)
- Thread starter MTNRAT
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- Thread starter
- #22
Here is the passage photoman refers to. Thanks.
The fan clutch is a small fluid coupling with a thermostatic device and controls a variable-speed fan. It ensures that the fan will rotate at just the right speed to keep the engine from overheating, and reduces drive to the fan when it is no longer needed. The fan clutch has a fluid coupling partly filled with silicone oil designed for just that purpose. When the temperature of the air passing through the radiator rises, the heat alerts a bimetal coil spring to "uncoil" or expand. When it expands, it allows just a little more oil to enter the fluid coupling, so the fluid coupling starts to rotate the fan. If the air coming through the radiator is cool, the opposite happens; the coil spring contracts, the oil leaves the fluid coupling and the fan slows. Slowing the fan when it is not needed reduces fuel consumption, makes less noise and saves engine power. Sometimes a flat bimetal strip spring is used instead of a coil spring; it bows out and in when the temperature rises and drops, letting oil in and out of the fluid coupling.
Cheers,
Sean.
The fan clutch is a small fluid coupling with a thermostatic device and controls a variable-speed fan. It ensures that the fan will rotate at just the right speed to keep the engine from overheating, and reduces drive to the fan when it is no longer needed. The fan clutch has a fluid coupling partly filled with silicone oil designed for just that purpose. When the temperature of the air passing through the radiator rises, the heat alerts a bimetal coil spring to "uncoil" or expand. When it expands, it allows just a little more oil to enter the fluid coupling, so the fluid coupling starts to rotate the fan. If the air coming through the radiator is cool, the opposite happens; the coil spring contracts, the oil leaves the fluid coupling and the fan slows. Slowing the fan when it is not needed reduces fuel consumption, makes less noise and saves engine power. Sometimes a flat bimetal strip spring is used instead of a coil spring; it bows out and in when the temperature rises and drops, letting oil in and out of the fluid coupling.
Cheers,
Sean.
Oh great, we are all at the mercy of some little bi-metal spring. And 6 to 12 year old little bi-metal springs, no less. Six to 12 years in bi-metal spring years is probably about 90 years in human years. I forget the exact formula.
Let's hope they remember when to coil or uncoil, or even why they are supposed to coil or uncoil...
Ed
Let's hope they remember when to coil or uncoil, or even why they are supposed to coil or uncoil...
Ed
Ed,
I just took my old clutch apart. It is very interesting inside. the bi-metalic spring is hooked to a flat bar that blocks off two holes near the outer edge of the housing. I very scientificaly heated the housing on my stove burner (the wife's at the store at the moment
) and the bar pivots to open the passages. I had to get it quite warn for this to happen and the clutch had silicone in it and very little indication of any leakage. I imagine that wear and tear on the spring is most likely why they start to fail as opposed to leakage.
Dan.
I just took my old clutch apart. It is very interesting inside. the bi-metalic spring is hooked to a flat bar that blocks off two holes near the outer edge of the housing. I very scientificaly heated the housing on my stove burner (the wife's at the store at the moment
) and the bar pivots to open the passages. I had to get it quite warn for this to happen and the clutch had silicone in it and very little indication of any leakage. I imagine that wear and tear on the spring is most likely why they start to fail as opposed to leakage. Dan.
- Thread starter
- #25
Exellent work Professor.
Sean
Sean
Dan, you just reminded me that I have my old fan clutch. I had thrown it in the garage and since I haven't tripped over it yet, I forgot about it. I'm going to perform an autopsy and check out it's innards.
Ed
Ed
