Reduce AIO Liquid Cooler Noise and eliminate Pump Whine

General

Liquid cooling solutions have been making an increasing appearance in the cases of many PC enthusiasts lately. This is probably mainly due to the fact that all-in-one (AIO) liquid coolers are almost as easy to install as conventional air coolers. An AIO liquid cooler is a sealed system that comes already pre-filled at the time of purchase, where a heat sink with an integrated pump is connected to a radiator with two hoses. So, no cooling liquid has to be filled in, but the heat sink has only to be installed onto the CPU (or GPU) and the radiator in the PC case. AIO liquid cooling solutions take up less space in the direct vicinity of the CPU and thus leave room for other components. In addition, the tidier interior is especially popular among PC owners who run cases with a transparent side panel. A disadvantage in this context may be that the air flow that is normally produced by the conventional fans on the CPU coolers is missing, which one would normally be able to use in conventionally cooled systems to cool the voltage regulators or RAM modules with.
In this section, I will mainly focus on AIO liquid cooling systems, although most of the explanations will in principle also remain valid for models with an external pump.

The Cause

For normal liquid PC coolers, we also have to consider several independent causes for the emission of noise. First, as with the graphics card and the case itself, there are the fans that provide the necessary air flow for better heat exchange at the radiator. The points of view on the subject of fan noise do not differ from those that I have already described in detail in the section dedicated to this subject and I will therefore not go into it again here. In addition to the noise caused by the fans, there are two other sources of noise for liquid coolers. On the one hand, there is of course the pump noise, but even in 'high flow' configurations (i.e. where the pump is operated at high speed) the pump usually operates relatively silent. But there is a second source for noise in liquid cooling systems, which almost always can be eliminated completely with the right setup: the gurgling and bubbling of the coolant or the howling of the pump. So I will first briefly discuss the normal operating noises of the pump and then turn to the second cause in the rest of this part of the guide and help you to get these noises under control.

The Remedy

As just mentioned, the noise of the pump itself is usually of rather secondary importance. Even if you can occasionally read on the Internet that cooling with a lower pump speed works better, because then the water has 'more time to cool the CPU' due to the slower flow speed, this statement is just plain wrong (and almost painfully so). The cooling performance of a water cooling system is better, the higher the flow velocity of the cooling medium is. As with fans, the same applies here: higher pump speed, better cooling performance, but also more noise. On the other hand, liquid cooling systems, if properly installed, are already very efficient cooling devices even at low pump speeds. So, except for overclockers, a medium or low speed should be sufficient to keep a CPU or graphics card within the permissible temperature range. But of course it never hurts to measure and keep a look at the CPU temperature. Or maybe even control the pump speed dependent on the CPU temperature with a program like Argus Monitor. But as just mentioned, for the pump speed and regarding noise this is rarely really necessary.

The second cause is much more annoying, but fortunately you can usually eliminate this kind of noise completely. Unfortunately, there are indeed many installations of AIO liquid coolers, which are characterized by a more or less noisy bubbling or gurgling of the coolant which might in extreme cases even be accompanied by howling pump noises. Probably by then your first thought might be: "OK, that must be like liquid cooling systems sound like." or even: "Damn, the pump of my AIO is broken. I guess I'll have to replace that unit." And more often than not, that's not the case, but they cause by mistakes that were made during installation and which can be fixed rather easily. So, what exactly is 'broken' here and how do you get the AIO as quiet as it should be.

The cause of this type of noise is almost always the air that is inevitably present in any AIO. Even right after purchase, 2%-10% air in the system is normal, and over time, this decreases percentage increases even more due to permeation. And this trapped air will always rise and gather at the highest point in the cooling loop. The gurgling and bubbling will occur when this air is entrained by the flow of coolant and then rises back up through the radiator. The howling of the pump in turn indicates that there is an air bubble inside the pump, causing its speed to fluctuate. Some pump models also use the coolant to lubricate the pump itself. If this is the case, not only will the pump whine annoy you in the short term, but soon you will also have to invest money in a new cooling solution. With other models, this is not a problem with regard to the durability of the pump, but the pump noise is still annoying and of course the cooling performance of such a system is extremely limited, meaning that the CPU will quickly reach Tjmax and either the system shuts down altogether or at least clocks down, which will be noticeable in a performance drop. Both then lead many users to the assumption that the AIO cooling system would be defective, whereas the cause here is actually 'just' an incorrect installation.

So what do you have to consider when installing an AIO water cooling system? So, what now is the most common mistake and of course above all: How do you install an AIO liquid cooling system correctly?
As already mentioned, you must ensure that the pump is not at the highest point in the loop. In general, most common mistake when installing an AIO cooling system is that the radiator is installed at the bottom of the case. This placement is to be avoided at all costs, because that way the pump — which is located in the CPU heat sink — will always be at the highest point and it is, so to speak, ensured that the air in the cooling system will find itself exactly at this point. A bad cooling performance and in almost every case also pump noise are guaranteed in this constellation.
As far as themals are concerned, then the most favorable installation of the radiator would be at the front of the case at the intake side of the case, but also the installation at the outlet (usually in the top of the case) is possible. When installing the radiator in the front of the case, the hoses of the cooling system should be at the bottom end of the radiator, if possible. Only if that is not possible — e.g. due to too short hose lengths — one can install the radiator also in such a way that the hoses are on the top end of the radiator, but you must then ensure that the upper edge of the radiator lies still clearly above the pump.

Date published: 16.06.2021

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Author: Udo Rietschel

Written by Udo Rietschel

Udo is one of the two founders of Argotronic UG (haftungsbeschränkt). He is writing software since he got his hands on his first computer (a ZX Spectrum 48k back in 1988, while living in the GDR; a country that does not even exist anymore -- much like his ZX Spectrum).
Today, he is working as a software engineer, creating software for autonomous vehicles as well as Argus Monitor, which is — in his (biased) view — the best fan control software for Windows.