Started the car, put it in park and let it get up to temp. I could easily stop the fan
What does that mean?
How hot was the engine/rad? was the rad hot down below not just at the top?
fan only kicks in when needed, i.e. viscous element heated up
Viscous fan from RAVE
There are two main components of the viscous fan
drive : An input (drive) member consisting of a
threaded shaft passing through a bearing into the
clutch plate and secured to the water pump. An output
(driven) member comprises the main body to which
the fan attaches, with the temperature sensing
mechanism (bi-metal coil) and pump plates.
The fan drive only has to be engaged periodically,
between 5% and 10% of the time during normal
driving conditions, because usually the vehicle is
cooled by ram air.
A bi-metal coil senses air temperature behind the
radiator. When a pre-determined temperature is
reached, the coil opens a valve which allows fluid to
enter the drive area. Centrifugal force circulates the
fluid to the annular drive area. There are two sets of
annular grooves, one in the drive clutch and the other
in the drive body, a specific clearance being provided
between the two sets of grooves. When this clearance
is filled with viscous fluid a shearing action, caused by
the speed differential between the two drive
components, transmits torque to the fan. The fluid is
thrown to the outside of the unit by centrifugal force
from where it is then re-circulated to the reservoir via
the pump plate adjacent to the drive member.
If the engine speed is increased, the amount of slip
will also increase to limit the maximum fan speed.
When the air temperature from the radiator drops
sufficiently, the bi-metal coil closes the valve and
prevents fluid entering the drive area, see 26M7026.
The fluid that is in the drive area will gradually pump
out into the reservoir and the fan will return to an idle
condition.
