Fan Clutch Problem

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phi - 16 Oct 2006 22:34 GMT

I have a 1995 BMW 740iL, a couple of days ago as I drove on the
interstate, I heard a loud humming sound that only got worst as I
accelerated, I thought it was the transmission, yet the gears engage
correctly. So I stopped at a mechanics and he came to the conclusion
that it was the fan clutch that it was locked.
The question is will a bad fan clutch make a loud humming sound, it
sounds as if the engine were being stressed out, yet it drives fine and
the transmission is engaging correctly.
Can anyone shed some light?

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Josh Assing - 16 Oct 2006 22:47 GMT

yes

>I have a 1995 BMW 740iL, a couple of days ago as I drove on the
>interstate, I heard a loud humming sound that only got worst as I
[quoted text clipped - 5 lines]
>the transmission is engaging correctly.
>Can anyone shed some light?

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Dave Plowman (News) - 16 Oct 2006 23:20 GMT

> The question is will a bad fan clutch make a loud humming sound, it
> sounds as if the engine were being stressed out, yet it drives fine and
> the transmission is engaging correctly.
> Can anyone shed some light?

The fan clutch has nothing to do with the transmission - it's a viscous
coupling (clutch) to the radiator cooling fan which should progressively
lock up if needed on hot days, etc, thus only spinning the fan fast when
needed. This saves both energy and noise. And they can fail in the locked
state. It's easy to check. With the engine cold and not running, try
spinning the fan by hand. When working correctly it will spin freely.

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