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Re: Fan clutch urban legends
Dave,
You did warm up your engine to operating temp before performing the
newspaper fan clutch test, didn't you?
Because otherwise your test is invalid as are you conclusions.
The fan clutch is connected to the water pump via a viscous clutch fan. As
temperatures rise, the viscous clutch firms up and the fan's speed begins
to correlate with that of the engine. When the engine is still cold (no
extra cooling required), the fan clutch is largely slipping and one can
stop it with a rolled up newspaper.
The most common failure mode of a viscous clutch fan is a fluid leak. Thus
the newspaper test to see if the clutch still engages when the engine bay
is hot. If it doesn't, all the fluid has leaked out and you need a new
clutch that is sold separate from the fan blades.
alex f
|---------+--------------------------->
| | "David A. |
| | Leonard" |
| | <dleonar1@maine.|
| | rr.com> |
| | Sent by: |
| | owner-bmw@digest|
| | .net |
| | |
| | |
| | 02/20/02 11:52 |
| | PM |
| | |
|---------+--------------------------->
>---------------------------------------------------------------------------------------------------------------|
| |
| To: <bmw@domain.elided> |
| cc: |
| Subject: Fan clutch urban legends |
>---------------------------------------------------------------------------------------------------------------|
The " rolled up newspaper in the fan clutch test is bunk!
I tried it with a brand new clutch..you can stop this one too!
These fan clutches actually are not thermostatic.. they simply spin at a
percentage of the pully speed..something like 60% at higher rpms, and less
at idle.
Try it with a new clutch and see.
Dave Leonard
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