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View Full Version : Engive RPM Vs Cooling Fan Speed

Spooks
20-06-2006, 09:03 AM
Good morning all,

On a couple of occasions ive experienced a ‘whooshing’ noise when accelerating (and when blipping the throttle when stationary) so I popped the bonnet last night. After having a look about and when my girlfriend arrived home to blip the throttle, I noticed that the cooling fan would get faster as the engine RPM increased making one hell of a ‘whooshing’ noise.

The engine was up to temperature at the time after a drive home from work. Does anyone know if this is something it should do or some kind of electrical gremlin ??

Thanks
Ian

Ps…..it’s a 2002, S54
c_w
20-06-2006, 10:19 AM
It's a viscous fan which spins slowly when the engine is cool or normal operating temp but if it gets a bit hotter there is a clutch that locks in the fan and it runs with engine speeds and sounds like pretty loud.
spunkym
20-06-2006, 03:04 PM
Yeh, I have also been aware of this on my S54 MR. I thought it was diff noise at first (sounds a bit like the whine you hear from a bus when it pulls away) but then noticed that you only hear it on hot days when the engine is warm. It's quite normal.
Spooks
20-06-2006, 04:55 PM
Well I’ll keep an eye (or ear) on it and make sure its only doing it when its hot.

I always thought it sounded like a plane on takeoff when accelerating before but when that fan gets spinning even faster im surprised it didn’t actually lift off !!

Thanks for that guys.
spunkym
20-06-2006, 05:52 PM
The fan still spins when the engine is cold but only via a fluid (viscous) coupling. It's quite easy to stop the fan even with your hands but watch your fingers on the fan blades!

It's really only when the viscous is locked (magnetically I'm guessing) that it spins with any kind of vigor and I think this is probably when you can hear it.
M3 Compact
20-06-2006, 06:38 PM
The fan still spins when the engine is cold but only via a fluid (viscous) coupling. It's quite easy to stop the fan even with your hands but watch your fingers on the fan blades!

It's really only when the viscous is locked (magnetically I'm guessing) that it spins with any kind of vigor and I think this is probably when you can hear it.

You should be able to do this (http://media.putfile.com/MOV0151818) when the engine's cold. Safer to try with a gently rolled newspaper if you're unsure about the coupling. :wink: