Author Topic: M42 radiator fan (Read 3374 times)

ozi_uki · « **on:** January 28, 2010, 04:47:24 AM »

Hello,

Could anyone please advise what is the logic of the radiator fan's operation?
Is it engaged all the time?
Does it spins faster with the higher revs?

I am pretty sure that with higher revs there was only engine's noise getting up. However, when I used the 318is last time, I noticed a clear hauling noise with the revs up.
Is this the way it is supposed to be?

Any advice will be appreciated.
Thank you!

Ozi Uki.

DesktopDave · « **Reply #1 on:** January 28, 2010, 08:55:16 AM »

The engine fan is driven by a viscous slip clutch, a bit like an LSD. The hotter it gets, the more it locks up & the fan spins faster. If the clutch is bad, it'll spin the fan but slip too much. I'd figure the clutch could also lock the fan...in that case you'd have the fan on full all the time. That would make a lot of noise.

You can test it. When your engine is stone cold the fan should spin with very little resistance. After a ride, when the car is warmed up, the fan should have much more resistance but still spin pretty easily.

If I had to estimate, I'd say a good hot clutch will resist turning the ends of the fan blades by maybe ten pounds. Cold, maybe a pound or two.

There's also an aux fan in front of the radiator. It should turn on low speed when the engine is slightly over halfway and high speed when the engine is really hot. The A/C will also turn that fan on.

ozi_uki · « **Reply #2 on:** January 29, 2010, 04:33:53 PM »

Hi, thanks for your clear and detail advice!
It sounds like the fan clutch is on all the time. Is it serviceable? I have got some mechanical and electrical repair background so it should not be a problem for me unless some special jigs are required.
Or should it be replaced?

Thanks!

4banger · « **Reply #3 on:** January 29, 2010, 04:39:46 PM »

id ditch the clutch fan for a 12v fan. i get mine here http://store.nexternal.com/shared/StoreFront/default.asp?CS=ireland&StoreType=BtoC&Count1=243496119&Count2=160636544 they come in 12 & 14in versions. i had a 12in one mounted to the front as a pusher on my DD for a while.

DesktopDave · « **Reply #4 on:** January 29, 2010, 04:53:25 PM »

IDK if they're serviceable. You can toss the clutch & bolt a new one into the fan disk, many BMWs use the same clutch. Replacing with an electrical fan is a pretty good idea too.

colin86325 · « **Reply #5 on:** January 29, 2010, 09:38:58 PM »

The fan clutch is not meant to be serviced. However, people have serviced them by drilling out the full plugs, draining out the old fluid, and refilling with silicone clutch fluid.
Never tried it myself though.

ozi_uki · « **Reply #6 on:** January 29, 2010, 09:55:31 PM »

Thanks everybody.
I've got a clear idea what to do now.

Let me try a let you know how did it go.

Cheers,
VL