Cooler Master Seidon 240M AIO Liquid CPU Cooler Review

Hi guys! Today I’ll be reviewing an AIO (All-in-One) Compact Liquid CPU Cooler from COOLER MASTER and its the SEIDON 240M model which is introduced after the following success with the Seidon 120M. This CPU Cooler is equipped with 2 x 120mm fans + integrated pump aka waterblock + 1 x 240mm radiator with pre-filled coolant sealed directly from factory for a free-maintenance operation for many years. So how does this cooler compete with the others in the saturated liquid cooling market? Before diving into the review, let’s briefly glance the specifications and overview of the features.


Model: RL-S24M-24PK-R1
CPU Socket: Intel LGA 2011-3 / 2011 / 1366 / 1156 / 1155 / 1150 / 775
AMD Socket: FM2+ / FM2 / FM1 / AM3+ / AM3 / AM2+ / AM2
Pump Dimensions: ø 70 x 27mm (ø 2.75 x 1.1 inch)
Radiator Dimensions: 273 x 120 x 27 mm (10.7 x 4.7 x 1.1 inch)
Radiator Material: Aluminum
Tube Length: 315 mm
Tube Diameter: Φ5.8
Fan Dimension: 120 x 120 x 25 mm (4.7 x 4.7 x 1 in)
Fan Speed: 600~2400 RPM (PWM) ± 10%
Fan Airflow: 19.17 ~ 86.15 CFM ± 10%
Fan Air Pressure: 0.31 ~ 4.16 mm H2O ± 10%
Fan Life Expectancy: 40,000 hours
Fan Noise Level: 19 ~ 40 dBA
Fan Bearing Type: Rifle bearing
Fan Connector: 4-Pin
Fan Rated Voltage: 12 VDC
Fan Rated Current: 0.2 A
Pump Life Expectancy: 70,000 hrs
Pump Noise: <25 dBA
Pump Rated Voltage: 12 VDC
EAN / UPC Code: 4719512040805 / 884102020049

Cooler Master Related Products

  1. Cooler Master Seidon 240M AIO Liquid CPU Cooler Review


1. Ultra-Fine Micro Channels: COOLER MASTER UltraFine Micro Channel with 2 times micro channel surface area transfers maximum heat between cold plate and coolant.
2. FEP Tubing: The FEP tubing has advantages of nearly no moisture absorption, high thermal stability and high pressure tolerance to enhance product life and durability.
3. Durable Ceramic Bearing: Ceramic bearing offers many advantages such as higher sped and acceleration capability, increase stiffness and lower friction, which resulting a durable and long life pump.
4. Zero maintenance: Factory filled with coolant, then sealed and pressure tested, the COOLER MASTER Seidon 240M requires zero maintenance for years.
5. Universal Socket Compatibility: The COOLER MASTER Seidon 240M features universal socket support including Intel LGA2011, 1366, 1156, 1155 and LGA775 as well as AMD FM2, FM1, AM3+, AM3, AM2+, and AM2.
6. Efficient Design for Overclocking: Performance 240mm radiator is designed to dissipate huge heat from overclocked CPU and can accommodate two 120mm PWM fans. The 120mm PWM fan offers a wide RPM range of 600~2400 +/- 10% allowing you to fine tune and balance fan noise and performance.


Packaging-1: Here I have the Seidon 240M Box that houses the awesome CPU Cooler. On the front, we can see an overview of the cooler (waterblock + radiator + dual fans) and some brief feature description. The box’s rear displays the dimension of the waterblock and radiator in millimeter. There are 8 languages (English , French, Spanish, Danish, Italian, Russian, Chinese and Japanese).

Packaging-2: Looking at the sides of the box, the left side from the front displays the specifications as I have listed above, and on the right side displays the inner view of the waterblock which wasn’t shown earlier from the front.

Packaging-3: Opening up the box reveals the plastic wrapped items tucked neatly in its own compartment. The waterblock along with the radiator takes up much of the space here. The anti-vibration pads is at one of the top corner wrapped in plastic.

Packaging-4: Here are all the accessories that comes with the Seidon240M. Starting from top left to bottom right, we can find a warranty paper, user manual guide, Intel and AMD Back plate + Retention Plate + 4 mini screws, Thermal grease, 16 x long screws (30.5mm) to support 4 fans sandwiching the radiator, 8 x long screws (33.5mm) to install 2 fans outside the chassis, 1 x Nut setter, 2-to-1 PWM adapter, 8 x medium screws for radiator installation.

Packaging-5: Here are the 2 x 120mm fans that comes along with Seidon 240mm. Each of this fan uses 4-pin (PWM) and fully braided and has black cable from the source to the pin which is very nice to see. Both fans are opened-corner which allows users to use this fan for something else with anti-vibration grommets if they were to swap the Seidon240M fans with something quieter like Noctua or something more flashier like Enermax L.E.D Vegas fans. This fan model is A12025-24RB-4CP0F1 aka DF1202512RFUN (DC, 12V, 0.37A) and has a cable length of 12 inches.

CPU Cooler Installation

Installation-1: Here is an overview of waterblock and radiator. The orange-base waterblock does not have a mirror finish to it though.

Installation-2: Install the mounting bracket to the waterblock using the 4 x mini screws.

Installation-3: Next, move on to installing the fans to the radiator. Ensure to get your anti-vibration rubber pads first! I missed this one out during my first installation. The user manual guide did not emphasize on this. Get ready the long screws (30.5mm in length)

Installation-4: Install the 2 x 120mm fans using the long screws. Ensure both fan cables are exiting from the same direction! The configuration of this fan placement is push-config (Pushing air to the radiator to dissipate heat from the aluminum fins.

Installation-5: Go behind your motherboard, and install the Intel/AMD Backplate (depending on your system whether its an Intel or AMD motherboard!) Fix the backplate by using 4 x standoff screws. Tighten them with a Nut Setter.

Installation-6: Mount the radiator to the chassis first. You can use the 4 x medium screws to secure it. If you are planning to add an additional 2 x 120mm fans for a push-pull config, you will need to use the long screws instead of the medium ones.

Installation-7: Note: You can install the cable first before installating the radiator as it might block you from connecting the fan cables to the motherboard. Next, apply the thermal paste provided by COOLER MASTER.

Installation-8: Finally, install the waterblock by screwing the applied mounting bracket to the backplate.

Cooling Performance Testing

Test Rig Configuration
CPU Cooler: Seidon240M
Processor: Intel Core i7 3770K
Motherboard: Gigabyte Z77X-D3H
Memory: G.Skill Sniper DDR3 1600MHz 32GB
Primary Hard Drive: Transcend SSD370 256GB
Power Supply: Rosewill Fortress 750W
Chassis: Fractal Design Define XL R2 Titanium + 3 x 140mm Fans

We ran the CPU stress test utility Aida 64 with the option ‘Stress CPU and FPU’ for heat and stability test from CPU with 2 CPU cooler for performance comparison:
1. Intel Stock Cooler
2. Noctua NH-D15 (2 x NF-A15 fans)

Our room temperature throughout the test is 30ºC in average and the stress test is repeated for several times in order to get a stable and consistent temperature reading. The final result is presented in the graph as below:

The initial run with with Intel 3770K stock speed reveals 3-5 degree Celcius difference on idle between the Intel Stock Cooler, Noctua NH-D15 and Seidon 240M. Upon loading Aida stress test, both aftermarket air + liquid coolers pull away quite a significant difference from the Intel Stock Cooler by a margin of 20+ degree Celcius.

Now for overclocking the Intel 3770K up to 4.2GHz, all coolers has slight increase in temperature by 2 degree Celsius. Turning on the Aida Stress Test again and we find that Intel Stock Cooler is approximately 95 degree Celsius, reaching almost 100 degree Celsius, which is quite a dangerous temperature level and isn’t great for longevity as it might cause heat issues for components nearby it. As for the remaining coolers, they are within the safe zone with 73 degree Celsius for Noctua NH-D15 and 69 degree Celsius for Seidon 240M for the OC Load Test.


The Seidon240M performance can be described in 1 word: “Amazing”. It’s able to quickly cool an overclocked CPU and maintained at a specific temperature while extracting the additional heat out of the chassis from other heat sources such as hard disk and graphic card. Upon shutting down the stress test, the temperature measurement instantly dropped to the idle temperature within split second for the Seidon 240M whereas the Noctua NH-D15 took a little longer (5-6 seconds) since the hot air is still trapped within the chassis and it depends on how many exhaust fans you have in the case. For the test, I’m using a case with 1 exhaust fan and 2 intake fans (all fans are 140mm).

One thing I found a little annoying is the noise emitted from the ramped up fan speed spinning around 1981 RPM (Revolutions Per Minute). The noise is similar to Intel Stock Cooler! Don’t take this as a negative way though as it can be useful to easily find out whether your CPU is on load or idle by listening to the sound without needing to above the chassis. Comparing against its CPU cooler competitor Noctua, Noctua NH-D15 is perfectly silent but a little hotter which is 4 degree Celsius. If you are thinking of buying a liquid cooler, I would recommend you this hassle-free watercooler if your computer case is able to support a 240mm radiator! If you are person who prefers a quiet environment like me, you can swap the original fans with 2 x Noctua NF-P12 (RM57).

Pros and Cons


  • Aesthetically pleasing to look at. Black theme matches any components in the case.
  • Solid build quality. Flexible and small diameter tubing.
  • Amazing cooling performance.
  • Works as a heat remover for all other components in the chassis.
  • Exhaust heat from computer case instead of within like most air CPU cooler which can be detrimental to computer components such as HDD, GPU.
  • Provides more room and better RAM (memory stick) clearance compared to air coolers. Easier to work within the case too since there isn’t any large piece of metal (e.g. air CPU cooler) in the center of the motherboard.
  • AIO (All In One). Plug and Play!. No need to purchase individual items (e.g. water pump, tubing, radiator, coolant) to setup them later. No mess and save time.


  • Noisy Fans
  • Confusing User Manual Guide (it includes both Seidon 120XL and Seidon 240M, mix diagrams, prefer to have them separated)
  • A little trouble installing the anti-vibration pads with the fans.
  • Radiator aluminum fins easily scratch and bendable. Handle with care when installing/removing fans on top of it.
  • Uses a little more electricity to power-up fans and water pump compared to air coolers.

Other Notes

  • Not compatible with most budget chassis as they do not have 240mm slot above or sufficient clearance within to support a 240mm radiator.
  • Users who owns a computer case that does not allow a tall tower air cooler but has slot for 240mm radiator can possibly consider getting this!
  • Do a test run on the radiator/water-pump to check whether its fine or has any leaks before installing it into your PC!

Nice to Have

It would be nice to have a dust filter which can be placed on the fans that is pulling cool air in to avoid dust accumulating on the radiator aluminum fins. It’s a pain to clean them since we will need to remove the entire liquid cooler and unscrewing the fans to dust it unless your chassis has very good dust filtration system.

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