Jim, the fan WILL "turn easier" (coast)...June 21 2012 at 2:30 PM
|Randy Millard (Login Henrysnephew)|
Response to This makes no sense to me....
when cold - but not at first. The fan clutch unit is filled with a silicone based fluid that settles to the bottom of the housing when the unit is stationary - when the engine is first started the "puddled" fluid is distributed outward by centrifugal force and creates drag between the halves thus turning the fan. After the engine has run for 20-30 seconds the fluid has time to be redirected towards the center of the unit and the fan "freewheels" - this is why you'll hear the fan "roar" at first after startup, but then it diminishes rapidly. The coiled heat-sensitive spring on the front of the housing turns an internal valve that controls where the fluid is allowed to migrate to (again, by centrifugal force) depending on the amount of heat the spring "feels". Hot air heats the spring coil, spring coil turns the valve, valve directs fluid outward within the housing to create the "coupling" effect needed to drive the fan at (or near) the hub speed. Hard to describe, but actually a simple design. Randy Millard (Henrysnephew)