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Why Is My AIO Making a Gurgling or Rattling Noise?
Short answer: A gurgling or bubbling sound usually means air has worked its way into the pump. It is fixable at home by releasing the pump cap and shaking it so the air moves back into the radiator. A rattling or clicking sound is more often a fan than the pump. A high-pitched electrical whine is normally coil whine, which is harmless.
Not every noise coming out of an AIO is a dying cooler. The sounds are distinct, they have different causes, and most of them have a fix you can do yourself in about fifteen minutes. Here is how to tell them apart.
Identify the noise first
| What you hear | Most likely cause | Is it a problem? |
|---|---|---|
| Gurgling, bubbling, trickling water | Air trapped in the pump or moving through the radiator | Fixable, worth addressing |
| Rattling, clicking, buzzing | Usually a fan, not the pump | Check the fans first |
| High-pitched electrical whine | Coil whine from the pump motor | Normal |
| Grinding, or noise that worsens over weeks | Failing pump | Contact support |
Start with the fans, not the pump
A clicking or rattling noise is far more likely to be coming from a fan than from the cooling pump. Fans are the cheaper and easier thing to rule out, so do that first and save yourself pulling the cooler off your CPU for nothing.
The test is to stop the fans one at a time and listen. If your fans run on a CAM-controlled header, open the Cooling tab in NZXT CAM, select the fan, set the mode to Custom, and drag the right-hand point of the curve to the bottom to stop it.
If the fans are not on a CAM-controlled header, you can gently press on the centre hub of the fan until it stops spinning. Press the hub, never the blades.
One important exception. Do not manually stop high-performance fans such as the NZXT Performance Series F120X or F140X. These fans carry enough force to cause serious injury. Stop those through software or by disconnecting power, never by hand.
If the noise disappears when a particular fan stops, that fan is the culprit. If it is an NZXT fan, contact our support team about a warranty replacement.
Is a high-pitched whine a problem?
Usually not. A high-pitched buzzing or electrical sound from the pump is typically coil whine, caused by electrical current passing through the electromagnetic coil inside the pump. It is a normal characteristic of the hardware and it is not a sign of failure.
Where it is worth investigating is if the whine is extremely loud, which can point to a power delivery issue rather than the cooler itself. Two things to try:
- Move the cooler to a different power connector from the power supply, ideally one that does not have other devices sharing it.
- Add a UPS with power conditioning between the PC and the wall outlet.
Confirm the noise is coming from the pump
If the fans are ruled out, the most reliable test is to change the pump speed and listen for the noise changing with it. On CAM-powered Kraken coolers, set the pump mode to Custom and drag the right-hand point of the curve as low as it will go. If the noise changes, the pump is your source. If it stays exactly the same, something else in the system is making it.
Not every Kraken is CAM-controlled. The Kraken Core, Kraken 120 and Kraken M22 do not offer CAM pump control, and we do not recommend running their pumps below 100% for any length of time, because sustained low pump speed shortens pump life. You can drop the speed briefly in your motherboard BIOS to test for noise, then put it straight back.
How to clear air out of the pump
This is the fix for the classic gurgling AIO, and it works more often than people expect. You are not opening the loop or refilling anything. You are simply tipping the pump so the trapped air floats back up into the radiator where it belongs.
Step 1: Release the pump cap from the CPU
Power the system down fully and disconnect it from the wall. Disconnect the cables from the pump cap so it can move freely. Many Kraken coolers use detachable breakout cables that unplug at the pump itself. Models with integrated cables need to be disconnected at the motherboard or controller instead. The Kraken Elite (2024) has its breakout cable at the radiator, so nothing needs unplugging at the cap.
Remove the thumb screws holding the cooler to the socket. Most models use four. Some use two, and on those the screws only need loosening rather than removing.
Do not touch the thermal compound on the pump cap or the CPU.
Step 2: Shake the pump cap
Hold the pump cap below the level of the radiator and shake it firmly for 30 to 60 seconds. You do not need to remove the radiator from the case. In a compact build you may find it easier if you do.
Step 3: Reinstall the pump cap
Seat the cap back on the CPU and tighten the thumb screws evenly in an X pattern so the pressure across the CPU is even.
Step 4: Run it in
Start the PC and set the pump speed to 100% on CAM-powered coolers. Leave it running at that setting for at least four hours, and preferably overnight, before you change it back. This gives any remaining air time to settle out of the pump.
If some noise remains, run through the process again. There is often a second improvement on the second attempt.
When it is actually a failing pump
If the noise continues after two attempts at clearing the air, or if it is getting worse over time rather than better, that points to a failing pump. A pump that is on its way out cannot be repaired in place, so the cooler needs replacing.
Check your warranty before you buy anything. Get in touch through NZXT Support with your model and purchase details and our team will take it from there.
How to avoid this in the first place
Most trapped-air problems trace back to mounting position. If the pump sits higher than the top of the radiator, air in the loop naturally collects in the pump. Mounting the radiator in the top of the case with the fans as exhaust avoids this entirely, and a front mount works well too. Bottom mounting is the one to avoid. We cover the reasoning in full in our guide to AIO radiator placement.
Frequently asked questions
Is some noise from an AIO normal?
Yes. Every AIO has a small amount of air in the loop by design, so a faint trickling sound, particularly in the first days after a fresh install, is expected. Coil whine from the pump is also normal. Persistent loud gurgling is not.
How long should the gurgling last after a new install?
It commonly settles within the first few days as air finds its way into the radiator. If it is still there after a week, run through the pump cap shake above.
Can I refill or top up my Kraken?
No. NZXT AIO coolers are sealed units and are not designed to be opened or refilled. Opening one will void the warranty and is very likely to make things worse.
Does lowering the pump speed reduce noise?
On CAM-powered Kraken coolers you can lower pump speed, and it can reduce noise. On the Kraken Core, Kraken 120 and Kraken M22 we do not recommend running below 100%, because it shortens the life of the pump.
Will running the pump at 100% all the time wear it out?
No. Kraken pumps are designed to run at full speed continuously. Running at 100% is the safe default, and it is what we recommend after clearing air from the loop.
Still hearing it?
If you have worked through the fans, the pump speed test and the air-clearing steps and the noise is still there, talk to us. Head to NZXT Support and we will help you figure out whether it needs replacing.
