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When people think of external radiators for PC watercooling, the MO-RA from Watercool is usually on the top of their mind. A massive behemoth of a radiator, it has undergone several revisions and changes- some announced, such as when the MO-RA3 series took over from the MO-RA2 in 2011, and some silent, such as when there have been multiple difference MO-RA3 radiators that came out in the past 5 years with subtle changes that people were unaware of. MO-RA stands for Monster Radiator, and it is a fair name. So let’s thank Watercool for the test sample and see how this fares as an external radiator system, and also against other large but more traditional radiators.

The MO-RA3 comes in various forms- core only, LT and Pro. The LT and Pro have a shroud around the core and differ only in terms of fan mounting- the Pro offers fan mounting on both sides of the core whereas the LT only comes with single side fan mounting out of the box. The other main distinction is in terms of the core size itself, with the MO-RA3 360 and MO-RA3 420 being the two options available. The former is a 3×360 (9×120) mm fan square radiator and the latter a 3×420 (9×140) mm fan square radiator. Other options are merely cosmetic with a standard black, a powdercoat white and a polished stainless steel to choose from. We take a look at the stainless steel MO-RA3 140 Pro here, beginning with specifications from the product page:


  • Material core: Copper (tubes), aluminium (fins)
  • Material casing: polished stainless steel
  • Dimensions (L x W x H): 475.5 x 430 x 65 mm
  • Weight: approx. 7700 g
  • Pressure tested: 5 bar
  • Threads: 6x G ¼” (DIN ISO 228-1)


  • 1x MO-RA3 420 PRO stainless steel
  • 4x Screw Plug G ¼”
  • 4x Spacers M4x20 mm
  • 1x Fan bracket and fan mounts for 140 mm fans
  • 1x Screw kit for 25 mm heigh fans
  • 1x Manual

There have been small changes to the fan mounting system even within the MO-RA3 era as mentioned before, and I do happen to also have a slightly older MO-RA3 420 Pro to compare to. These are huge radiators as-is, weighing close to 7.7 Kg (17 lbs) and measuring in similar to 3 65 mm thick triple 140 radiators stacked on top of each other. The MO-RA3 uses round copper coolant tubes and so offer higher pressure rating (most flat tube radiators are rated for 2-3 bars) but it is not really going to do much for end users who will operate their loop at 1 bar once all air is bled and there is no over pressure. The fins are alumunium (aluminum) but the coolant does not get in contact with the fins, and so aside from potential contact corrosion (which has not happened in any units in the last 5 years that I know of, so it’s a non issue) there is no issue of aluminum and copper in the same loop here- use without worry. One piece of information not available here, but seen in the provided manual, is that the radiator is rated for 80 °C which is very good, but you will have other components failing if your coolant is hitting this temperature anyway. Let’s take a look at the radiator, and more, on the next page.

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