iMac 27 mid 2011 cooling mod?

[decat]

Hi Maccers,

We got a 27" mid 2011 and some days ago the GPU to take it's retirement. The new GPU arrived, iMac is dismantled and before mounting everything back in it's place I'm trying find out how to improve it's internal cooling. Is there anyone here who added extra fans or did something else?

Since the superdrive bay is empty the GPU heatsink's underside is open / accessible so I trying to find out if it would be a good idea to mount 2 small 40x40x10 fans or 2 small blowers on it. These would would push the air up through the fins of the heatsink leave the iMac on it's upper side and would keep the temps of the GPU some degrees cooler/

A second thought is to mount two similiar fans (maybe 30x30x10) on the underside of the two ssd's located in the drive bay.

The fans are somewhat easy to find, what I don't know yet is how to power them.
So, is there anyone here who did some kind of mod? And if so, how did you power them?

Thanks in advance.

 

[USB3foriMac]

The GPU heatsink has a temperature sensor. So by right, the GPU should never overheat.
So let's assume it does;
1. You can use Macsfancontrol to set a lower temperature limit. This will make the fan spin faster.
2. If you add more fans, I doubt this will have any impact. Reason: the air inlet is relatively small and obstructed. Apple have done their best to maximize aiflow by a specifically designed fan, and having a fan of excellent quality (with double bearings, brush-free). So even you add fans after the original fan, you don't get any more air, but instead will have plenty of noise, and your fans may even obstruc the airflow as right now without ODD, the airflow is straight to the heatsink and out on top.

 

[decat]

I've seen temps of the failed GPU above 90° by just watching something on youtube so trying to keep the replacement a bit cooler is not a bad idea. It might not work, but it could too. I've searched the net for several days and couldn't find much info about placing extra fans. Just a video of a guy who used a CNC machine to make the outlet a bit bigger.
The inlets are indeed small, but since there's no ODD fresh will be sucked in through the opening of the ODD.

When members ask questions in the GPU upgrade topic sometimes the answer is that if they want to try something which hasn't been tested before they need to try it by themselves.

If it fails it fails, if it works...

 

[USB3foriMac]

Whenever I remove the ODD, I always tape the slot for two reasons:
1. you are not tempted to stick your SD card into that slot...
2. the air that comes from the fan should take the path along the GPU heatsink and out on the top. If the ODD slot is open, a significant amount of air will go out of (rather than come in from) this slot, as the fan sucks the air from the bottom and pushes it towards the GPU. Hence, in the area of the ODD drive will be a positive air pressure, so that some air will go out that slot and less air will go through the heatsink, so your GPU is even less cooled.
I do not really see a way to add standard fans, unless tiny ones that aremounted in the direction of the airflow, but that will be extremely loud.

 

[decat]

The fans I plan to mount are small and silent, no 120mm x 120mm standard fans.
Small: 1.57" x 1.57" / 40mm x 40mm and 1.18" x 1.18" / 30mm x 30mm
Silent: around 20dBA or even less

Something like these:

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2 of those on the gpu heatsink pushing the air coming from below through the heatsink and also two of those doing the same pushing the air coming from below through the hdd case & between 2 ssd's.

I don't really see a disadvantage in trying this, maybe the noise yes but the iMac is mostly used when doing music stuff so.

btw: checked your USB3 mod topic, really cool! Looks like I might tap power from a sata port but doing so I'll need to look out for 5v fans instead of 12v.

 

[USB3foriMac]

2 of those on the gpu heatsink pushing the air coming from below through the heatsink and also two of those doing the same pushing the air coming from below through the hdd case & between 2 ssd's.

Yes, they might indeed fit. Small fans normally don't have much airflow though, so it's probably worth a try whether this arrangement in conjunction with the existig Apple fan can really bring down the temperature.

btw: checked your USB3 mod topic, really cool! Looks like I might tap power from a sata port but doing so I'll need to look out for 5v fans instead of 12v.

Thanks. You can grab 12V from the HDD connector. The ODD SATA connector has 5V only (see this post here), but the HDD has 5V and 12V. Easiest would be SATA power splitter. You can also get SATA to Molex, as your fans have a 4-pin Molex attached.

 

[decat]

Fans & splitters etc have arrived.
iMac will be reassembled soon, took it apart to mount a working GPU.
Will try to some test with & without the extra fans running & will come back to you guys later.

 

[jsusa]

So, I am just curious.
What is the result?

 

[decat]

We are also renewing our attic which consumes alot of my time, on going since may.
But I did some testing after mounting the Quadro k4100m, but just some quick tests.

USB3foriMac said there would be some noise, yes there is.
Quite normal when you add 3 fans, 2 spinning at 5000 rpm, 1 at 6000 rpm.

One fan blowing directly on the GPU, the second one pulling air from the GPU pushing it to the HDD compartiment.
The third fan was pushing air through the GPU heatsink.

Since it's a GPU with custom BIOS it's not possible to monitor it's main temp but you can monitor the PECI.
The difference in temp with our without fans was about 15 to 20 degrees, GPU with fans stayed around 40 degrees while doing benches.

But these were quick tests, still have to do some more and fix the fans to the chassis etc.
Gonna remount this mac as stock and got me another one to test some more.

 

[Joakes02]

Hello! I am very curious on how you set it up. If you ever open it up again can you please post a picture! Thank you!

 

[decat]

Lol, they are still not in their final state. Been opening them once in a while to fiddle around. The renewing of our attic is finally reaching its final stage but the iMac's yet. Also been trying SSD's in RAID etc, too much at once.
While learning some soldering on a colleague's old laptop I was able to recycle a thin radial Sunon fan which might fit on the left side of the GPU, behind the wifi card.

The 40x40*10 fans are too thick, just a couple of mm. They cause pressure on the backside of the LCD.

What I did do while the iMac's are being used at the moment: cut a piece of cardboard big enough to cover the DVD drive compartment which is empty. The four sides the cardboard are taped, on the upper side to the heatsinks' support, left side to the air guide, bottom side to black plastic thing and right side to the chassis. Enough tape to make it airtight. All air goes to the heatsink and nowhere else. No pics though. As soon as there's an update I'll post it here.

 

[Nguyen Duc Hieu]

A cheap 2.5"caddy bay can be attached firmly in the place of the ODD and play the role of pressure wall nicely.

 

[ChrisCaro]

Follow up on this: did the odd removal and insertion of the cardboard "ducting" lead to significant benefit on gpu heatsink temps?

 

[decat]

This is how it looks. It ain't beautiful but I haven't seen temps above 60° when doing several Valley tests following up on each other.

 

[ChrisCaro]

Excellent, thanks for the follow up!

 

[Nguyen Duc Hieu]

This is how it looks. It ain't beautiful but I haven't seen temps above 60° when doing several Valley tests following up on each other.

Unless you want to install some other parts to the ODD position, I can't really see the benefit of removing it.

 

[decat]

Where would you have installed the SSD? In fact the plan was to install two SSD's and set them up in RAID. The 1TB HDD is still in use too. These plans have changed as I got me a Mini M1 & the 2 iMac's will be sold.

 

[Nguyen Duc Hieu]

Where would you have installed the SSD? In fact the plan was to install two SSD's and set them up in RAID. The 1TB HDD is still in use too. These plans have changed as I got me a Mini M1 & the 2 iMac's will be sold.

Use a cheap adaptor, you can install 2 x 2.5" SSD in the 3.5" bay of the stock HDD. I would move the 1TB HDD out of the iMac and put it in an USB enclosure. Not of much use for 1TB storage.

 

[bielousov.com]

Still not clear how you powered your fans, could you share connections photos please?
Also you might wanna try other Rom versions: I had 2 in my 780M, with one I had my heat sink at ~50–60C idle, and ~84C under load, the other one it's 64C top while benching and in the 40s idle. No other changes except the ROM.

 

[decat]

I didn't add extra fans, just taped the air wall and that's it. The 2 2011 iMacs here will be sold and I stopped investing time in them. I still like them, these are fun machines, run great for their age and still have some years to serve but do draw a lot of power from the socket.

I did try to install those fans though, the 40x40mm ones were slightly too thick to fit them in the case. They got power via a SATA splitter > Noctua fan controller > fans.

 

[ChrisCaro]

Here is my ducting,
Thanks Decat for the idea. Using this set up, with a high quality thermal paste, my GPU die temp does not rise over 52C when GPU is loaded between 80-100% with the ODD fan set at 100% speed. I see a 5C delta between heatsink temp and Die temp.

K4100m, 27", non-OC bios from nikey22.

 

[bielousov.com]

Ok, I just solved my overclocked 780M overheat with help from other folks in this forum.
Here's the original post: https://forums.macrumors.com/thread....1596614/page-522?post=29641774#post-29641774 but long story short: you in fact do need stuff in your ODD bay to build up air pressure.

In my case I had HDD there with some empty spots that were releasing the air from ODD fan on its way to the GPU heatsink. So I did a similar channel to the one above, but smaller and placed my HDD on top duct taping all holes in it.
Note: there's a clear airflow between the HDD and back wall, ~1in tall from ODD to heatsink.

The next cool find was that if you disconnect ODD temp sensor, the iMac would actually allow spinning the stock 2500rpm ODD fan all the way up to 3800rpm, so all you need to do is connect it with the heatsink sensor in FanControl to max out at 60°C and run those games in native resolution.

After the mod my 10% overclocked 780M (849MHz vs 758–797MHz) that has been crashing after 10 minutes full load (when heat sink goes above 77°C) is now stable and the heatsink doesn't heat up more than 62°C. With the stock frequencies I'm running even 5°C cooler, but who needs stock when overclock is stable, eh?

 

[ChrisCaro]

Ok, I just solved my overclocked 780M overheat with help from other folks in this forum.
Here's the original post: https://forums.macrumors.com/thread....1596614/page-522?post=29641774#post-29641774 but long story short: you in fact do need stuff in your ODD bay to build up air pressure.

In my case I had HDD there with some empty spots that were releasing the air from ODD fan on its way to the GPU heatsink. So I did a similar channel to the one above, but smaller and placed my HDD on top duct taping all holes in it.
Note: there's a clear airflow between the HDD and back wall, ~1in tall from ODD to heatsink.

The next cool find was that if you disconnect ODD temp sensor, the iMac would actually allow spinning the stock 2500rpm ODD fan all the way up to 3800rpm, so all you need to do is connect it with the heatsink sensor in FanControl to max out at 60°C and run those games in native resolution.

After the mod my 10% overclocked 780M (849MHz vs 758–797MHz) that has been crashing after 10 minutes full load (when heat sink goes above 77°C) is now stable and the heatsink doesn't heat up more than 62°C. With the stock frequencies I'm running even 5°C cooler, but who needs stock when overclock is stable, eh?

I dig the slick ghosted apple logo on your duct tape.

 

[decat]

Nice to see that the idea is being smoothened by others. As Ri7 mentioned in the GPU topic the other side needs to be looked after too. When the CPU is chill the PSU can still get a little hot, haven"t looked if something could be 'taped' in that area. When using TG Pro it's possible to add custom rules like (for ex: when PSU is at 45° CPU fan needs to run at 30%, when at 50° run at 55%, 53° at 65%, 55° at 75% and so on), rules can be adjusted to your likings and temperature observations. In most conditions the PSU stayed around 45°. Also had some rules for the HDD fan, as the GPU itself resides in the HDD compartment it ran at 30% when GPU reached 50°.

 

[decat]

So, some info regarding my own question back from the time when we used to search for stuff to kill time while being at home.

Two weeks ago I bumped on the M2 SATA caddy with a fan.

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Immediately ordered it and arrived after merely a couple of days.
The quality is flimsy, the aluminum case bends easy, but who cares, the caddy would be wrecked / modified anyway.

Also received a K4100m some days ago, flash was done yesterday and tested the card right after.
No screenshots available, was just some quick testing. Did two or three Valley benches and saw the heatsink + odd temp (sensor glued on GPU heatsink body) rise to 67 / 68 degrees C. The caddy was installed but not properly, the blower fan is open on two sides and took away the fresh incoming air from the odd chimney.

Today I did some Mc Guyver'ing using duct tape, mostly closing air gaps and also the inner side of the blower fan preventing it to take air out of the ODD chimney. The caddy itself was a bit modified too. Got no pictures available, but will make some in a week or two when I got more spare time available.

After the modifying, I did some Valley tests again.
When the first 3 Valley runs were done, the temps of the heat sink and odd stayed around 56 to 57 degrees C, a nice 10 degrees C lower.

I continued doing Valley runs for about 20 to 25 minutes, temps of heatsink and odd rose slowly to 62 / 63 degrees C.
These seem to be some nice results, and not too expensive to do.

The SATA slot has not been tested yet. I'll try to test this in the coming weeks and will also try to reopen the caddy to make pictures of what was changed.