27, 2009, 3.06 Core 2 Duo IMAC, will SSD solve the noise?

I'm building a customac soon and I'll need a second machine to use while it's processing files, looking around it seems my current 27 Inch 2009 Imac Core 2 Duo might be with keeping around, if only for the quality of the monitor, the performance will be fine for what I need.
I replaced the HDD with another and I am running HDD Fan control, the issue is that there is a low volume high pitched whirring sound from the machine that drives me nuts, I don't think there is anything abnormal about the machine and I'd guess 99% of people wouldn't notice it, but I'm a delicate flower.
The noise is always there, so if I have been away for a couple of hours and the machine has been idle, it's there.

My question is whether removing the HDD and inserting an SDD will likely change this noise, I'm not sure if it's just a fan running at a very low level or the HDD ticking over.

Opening up an iMac is not fun.
There is a video on tube showing how to check fan noise.
Essentially you can stop fan and also accelerate it.
Change in noise would indicate fan as source.
HD runs at constant speed.
Another test is run iMac off an external drive with internal HD unplugged.
This would isolate noise to fan.

I talked to someone who lubricated fan with 3in1 oil. Be very careful. NOT RECOMMENDED.
Cooling on iMac is complex. Do not unplug fan permanently. Even without HD it is probably necessary.

Places for parts and advice Powerbook Medic and Other World Computing

Thanks potemkin, sure is no fun opening them up, I still have a speck of dust on the inside of the screen from last time too.
I'll check out that video and try changing in an SSD before I put it in my new build.

Hi bobsbuddypeter, what hard drive did your 2009 iMac originally come with? Was it one of the noisy Seagate models and did you decide to replace it with a hard drive of a different brand? The temperature sensor cable in the 2010 model at least is brand specific; if you replace a Seagate drive with Western Digital, etc, you need a different temperature sensor cable or the fans run flat out and loud and some people solve that with third party fan control software or they order the appropriate HD temp sensor/cable or they pop to Maplin/RS and make their own, or they swap out the hard drive for the same HD brand as their model came with, being careful to make sure the sensor cable goes in the right way around or you're stuck with the same fan going flat out problem.

I fitted a 2TB Seagate and an SSD. The 2TB drive wasn't much quieter, so I decided to replace its mounting screws with silicone string and it made a difference, reducing noise transmission through the case. It sounded much more like an iMac should sound. I need to do a proper write up - I hesitated because in the end I dismantled it because I was worried the silicone string would perish/break or the knots would loosen and unravel; it gets so hot in there; I compromised and used silicone grommets that I made, not as good but a bit quieter than stock - but Apple's solution is perhaps more elegant. I'm told that when they finally did a recall of iMacs with the unsettlingly noisy tumble-rumble-bass Seagates, they replaced some of them with quiet laptop hard drives. I suspect they weren't 7,200rpm models. I would imagine that helped lower temperatures a bit, also.

I usually boot from my SSD but have Yosemite on both SSD and hard drive. The SSD read/write speed is disappointing and I have thought of getting a mini PCI-E SATA card so that I can get SATA III speeds, though that would mean surrendering airport and fitting a USB wi-fi dongle. Also, there is some debate as to whether it would work, some insisting it does, others not, and not enough posts from either camp. Still, boot up is quicker and apps certainly open faster, even under SATA II.

Using the hard drive as a storage drive and the SSD as my boot drive, it is much quieter as you can imagine. Temperatures are a little better but still nuts. I imagine the more recent iMac models with their cooler running parts don't heat up a box room quite like the 2010 model does.

If it turns out to be a worn out fan, I suppose you could try sewing machine oil, I'm not sure if the fans are sleeve or - I would probably use it as an opportunity to change out the fan for a new one. Though the 2009 and 2010 model are relatively straightforward to open up, if you are very careful with those ribbon cables (as I'm sure you know!), it's still not something we want to do too often, I feel. If fitting an SSD, there are several options; I would read up about best placement, re temperatures, as the route I went was a little different from one of the recommended ones. I can dig up a picture if it would help.