The Case of the Singing CPU Fan- Advice wanted

Mr.Fixit · TweakNOOB Joined: 20 Sep 2005 Posts: 21

I have an Epia M10000 that has been giving me trouble. Right now I am being driven crazy by the CPU fan which apparently sets up a piercing, high pitched resonance in the blades of the heat sink.

I originally thought it was the fan itself- the old one seemed to make the noise and it was plenty fried because the crappy Falcon case sets the CD right over the fan. So I drove round for a couple hours looking for a 40mm 3-wire and wound up paying $7- that's life in the boonies.

I installed the new one accidentally upside down (blows upward) - no noise. Discovered the mistake, installed it right side down- the noise is back as loud as before. Everything is clean as a whistle, tho it needed cleaning...

My Q is: what real difference does it make whether the air blows down into the fins or is sucked up thru the fins? Is there another tweak to try?

ps this sound is about as much fun as a dentist drill-

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fussnfeathers · Lord of the Tweak Joined: 14 Dec 2004 Posts: 2763

The CPU fan should blow AWAY from the CPU.........as you said, where it makes no noise. The idea is that heatsink fans pull the heat up, and the fan blows it away. If the fan is blowing back into the heatsink, all you're doing is blowing the hot air right back into the CPU.

Your "mistake" was the correct way.
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FreeTheRock [banned] · Posted: Wed Sep 21, 2005 12:26 am Post subject:

uh actually FNF that is the wrong way, you should always have the fan blowing down, when the fan is blowing down it cools off the heatsink, if the fan blows out it does not cool the heatsink, the heatsink is then not cooling down and staying hot and then your CPU will not get cool and you just made the CPU cooler completely ineffective. The idea of the fan is too cool of the heatsink not the CPU and if the heatsink does not get cooled it wont tranfer as much heat away from the processor.

HoseB · SirTweaksabit Joined: 03 Oct 2003 Posts: 260

Perhaps either way is OK so long as there is air flow through the case. My P4 2.6Ghz rig has no heat sink fan per se but rather only a case exhaust fan + PSU exhaust.

[TN] Nathan · ALMIGHTY PWNER! Joined: 14 Feb 2002 Posts: 7406

remove the fan and remove the sticker on the underside and drop a drop of motor oil on the bearing and work it in.

Then clean the surface, reattach the sticker and it should be a as good as new.
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fussnfeathers · Lord of the Tweak Joined: 14 Dec 2004 Posts: 2763

Yeah, I was a little tired when I posted that..........

It depends on how the case is set up. If you have a side-panel fan blowing air onto the CPU, then the CPU fan should blow down (into the CPU). If you only have front and rear fans, then it should blow away from the CPU, pulling the hot air away.

There's a debate on which is proper, it just depends on your setup.
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ToggleHead · TWEAKGURU Joined: 03 Mar 2004 Posts: 4360 Location: Jersey

[KoG]^weaZel · Posted: Wed Sep 21, 2005 12:12 pm Post subject:

the orientation of the fan depends on the heatsink design, whether or not a duct is being used and where the duct is leading to/from.

In his case the reason the fan is "screaming" is that with the fan pulling air from the underside of the cd-rom there is a vacuum being created. For sanity's sake I would mount the fan so it pulls air from the heatsink and keep an eye on the temperatures.
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fussnfeathers · Lord of the Tweak Joined: 14 Dec 2004 Posts: 2763

He's got a VIA cpu......they don't get all that hot.
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[TN] Nathan · ALMIGHTY PWNER! Joined: 14 Feb 2002 Posts: 7406

[KoG]^weaZel

Mr.Fixit · TweakNOOB Joined: 20 Sep 2005 Posts: 21

Actually it was Nathan who got me into this Very Happy

way back when this was a fledgling review site - I'm totally impressed !

Nathan answered my blind Qs about his Epia review so incisively (stuff about DDR at the time) that I went ahead and got one.

The case came with it- that wasn't his fault- I was too cheap to toss a 'working' case and had daydreams of building my own like some of you guys do.

Just FYI, no heat prob evident in the CPU - I can stick my finger on the heat sink anytime and not find it more than mildly warmish.

Not so with the PS. It's tucked up in a compartment that has fried 2 units- too hot to touch with the machine off- it's fan was actually blowing hot air onto the CPU fan when on, and overheating itself when 'powered down'.

That said- the M10000 board has worked flawlessly for me for 2 years as a daily use net workhorse- even with a wonky PS. It's own internal protection scheme saved everything by 'pulling the plug'.

It seems you all are saying that the fan can operate either way OK, with proper consideration to airflow?

Also want to thank you all for so many replies. I'm on a couple other forums where you could wait a week for just one. Thanks guys!

[TN] Nathan · ALMIGHTY PWNER! Joined: 14 Feb 2002 Posts: 7406

I would remove the fan and clean any dust on the blades and oil the sleeve bearing again and it will calm and quiet down.
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ToggleHead · TWEAKGURU Joined: 03 Mar 2004 Posts: 4360 Location: Jersey

fussnfeathers · Lord of the Tweak Joined: 14 Dec 2004 Posts: 2763

I agree with Weaz on this..........I did some digging on that particular case/mobo combo, and yeah, the gap between the CD drive and HSF is so small, that the fan is creating a "suction whine" trying to pull the air through the gap.

In this case, turn the fan around the "wrong" way, so it's blowing out from the CPU. Like I said, the VIA CPU doesn't get all that hot to begin with, BUT with the CD drive so close to the fan, even if it weren't making noise, the heat from the CD drive (when in use) is being sucked right into the HSF, and onto the CPU.

Monitor the temps, but I think you'll be fine.
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