Question replacing entire cooling in an iMac

Jan 23, 2020
Hi folks, I have an iMac (late 2012 fwiw) that gets too loud when the fans kick in (CPU temp goes to 100 C, fan RPMs go over 2500). The back story of this computer is that the original monitor stopped working and not wanting to pay the absurd amount of money to replace it, I "transplanted" all the guts to a box and bought a separate monitor. I included all the thermal sensors and everything.

The cooling setup is very simple, the fan cools two copper heat exchangers (one for the CPU and one for the GPU). See the pictures for details. The noise comes from the exhaust, which funnels down the air coming from the fan. I was wondering if any cooling experts here could recommend any parts that are higher efficiency and/or quieter. I'm up for replacing all the cooling parts, the only limitation is that one of them is sandwiched between the RAM and the motherboard (see second photo below), so I can't fit a regular fan on top of it.

Any ideas/brainstorming would be much appreciated.

I'd see if that shroud around the RAM is removable. A few mm can make a world of difference. A liquid cooler could probably fit for the CPU. Depending on the design. An air cooler may fit if the plate isn't oversized and the heat pipes are oriented away from the RAM. You'll need to take detailed measurements and compare to drawings from the manufacturers. Which many provide on their coolers spec pages.

Another issue is the hole spacing. Which is does not appear to be standard. You'd have to find a cooler with a sufficiently adjustable mounting bracket, drill holes in a bracket or worse fabricate a bracket. There's thermal adhesives but I wouldn't want something that permanent on a CPU. Plus I couldn't say how reliable they are.

The GPU is easier. Some aftermarket univeral GPU cooler will likely be fine. One which comes with separate adhesive VRAM heatsinks or buy them separately. Heat shouldn't be much of an issue as it uses a laptop GPU. Hole spacing is the biggest issue here too. It took me a while to find it. Something like the Zalman VF700 is likely ideal. But they can be pricey as they are discontinued. The offset design is the key point. Along with a fairly adjustable two point mount. Again you'd have to measure and find specs to be sure everything will line up and clear.
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