Provided by: Cooler Master

No compensation was received for review of this product.

Price Point

Price: $99.99 USD Retail

Class: Enthusiast

The Cooler Master Seidon 240M CPU Cooler is in the Enthusiast class of CPU coolers.


The Seidon 240M delivered excellent cooling performance under all conditions, the best we have seen from an AIO 240mm solution to date. The 240M also delivered the lowest noise levels of any of the 240mm units we have seen, delivering moderately quiet performance in day-to-day usage.

Reviewer's Opinion

I was always surprised that Cooler Master was not in the AIO Liquid Cooling market earlier, but by the same token, I was quite happy that they did not jump into the “me too” category of retreading the same OEM pieces that we have seen before. In Cooler Master fashion, they took their own route and came out with something decidedly different. While different is not always a good thing, in the case of the Seidon 240M, it is a very good thing.

One glance at the Seidon 240M lets you know that you are not looking at a cooler you have seen before. The pump and cooling block unit is an entirely different design than what we have seen previously. It is squatter, with more efficient side inlet/outlet placement and a very large copper contact plate. Cooler Master contends that the design is entirely their own, and I would not argue the point. It is sleek, well-engineered and obviously effective. An added bonus is the control software, or in this case, lack of. You can control the fans entirely with your BIOS/software, and set it up exactly how you like it in your system, and tweak all you like. It is a simple, effective, flexible solution.

Cooler Master makes quite a point of showing off the Ultrafine Microchannel design of the contact plate, and the theory certainly pays off in practice. The performance of the Seidon 240M was excellent all around, handling the high overclocks with ease, and easily bettering the more expensive 240mm units we have seen previously. Aside from the outstanding peak temperatures, the Seidon 240M also showed very quick cool down times with decreasing loads. There is no doubt that the Seidon 240M does an excellent job of dissipating heat on all ends, from the cooling block to the radiator.

Over time, the only complaint I have ever had with Cooler Master has been fan noise, so I was expecting the worst, given that 240mm AIOs tend to be the noisiest cooling solution imaginable. However, I was very nicely surprised when the Seidon 240M turned out to be the quietest 240mm solution I have heard to date. Make no mistake, when the fans are going full speed, the Seidon 240M is loud, but not the earsplitting volume we have seen from Corsair, the Tt Extreme and Antec 920 (not a 240mm, but the loudest of the bunch). After doing a little tuning of my fan control, in day to day activities, the Seidon 240M remained very tolerable, and around the middle of the pack from any type cooling solution. Even under heavy loads, the noise levels of the Seidon 240M were within expected limits. The great dissipation of the unit definitely helps in keeping the fan speeds and noise levels down, and makes the Seidon 240M a great 24/7 cooler.

The real kicker on the Cooler Master Seidon 240M is the price point; $99.95 MSRP. So, you get better cooling performance, less noise, easy installation and setup, and top notch build quality for less than what we have been seeing. There has to be a downside, right? Well, if there is, I can’t find it. Cooler Master may have been late to releasing their AIO, but they are still the old pros in cooling and the Seidon 240M showcases their experience and innovation. With all of this going for it, can we possibly give the Cooler Master Seidon 240M anything but our highest award?



  • Excellent Cooling at Idle and Full Load
  • Very Reasonable Noise for a 240mm Rad/Dual 120mm Fan
  • Excellent Cooling at Low Fan Speeds
  • Price Point Lower Than Direct Competition
  • Very Easy Installation In Cases With Proper Room
  • Easy to Work With Kink-Free Tubing
  • Maintenance Free
  • Unique Pump Design
  • Excellent Build Quality and Finish
  • Micro Channel Block Design
  • Pump Near Silent
  • High Overclock Easily Achieved While Keeping Well Within Thermal Limits



  • Loud At High Fan Speeds


Hi Tech Legion Editor’s Choice Award