The question came up again in a BGR explainer by Briley Kenney. It says most AIO coolers never need a refill, while custom loops "do require a coolant change every 12 to 24 months." That range is reasonable as a rough guide, but it isn't a rule. Two manufacturer documents show why: Corsair says about a year for its Hydro X loops, and Koolance says two to three years for its 702 coolant.
AIO coolers: the coolant isn't your job
BGR says AIO coolers come sealed from the factory, opening one would probably break something, and they can lose a little fluid over time without the owner needing to do anything. Corsair's own maintenance guide agrees on the main point. It says the AIO loop is sealed at the factory with as much air removed as possible, and that there's no maintenance for the liquid itself. Corsair also says plainly that you can't open the AIO and don't need to.
That doesn't mean an AIO needs no care. The work just moves from the liquid to the airflow. Corsair recommends:
- Clean the radiator. The fins are packed tightly, so dust and pet hair collect there. You may need to take the fans off to reach the hidden spots.
- Every two to three months if you live somewhere dusty, have pets or smoke indoors.
- Twice a year in a relatively dust-free room.
If your AIO is running but the PC still overheats, Corsair's support steps are, in order: clean dirt and debris off the fans and radiator, reapply thermal paste (Corsair suggests every 12 to 18 months), and if the cooler has a 3-pin header and no SATA connector, set that BIOS header to its fastest setting. Corsair also warns that opening or modifying the cooler voids the warranty.
These intervals are Corsair's recommendations for Corsair products. Other AIO makers may say something different, so check your own model's documentation. "No coolant maintenance" doesn't mean the cooler lasts forever, either. Neither BGR nor Corsair gives a service life for AIOs or a rate at which coolant evaporates.
Section summary: With an AIO, keep the radiator clean, keep the thermal paste fresh and leave the sealed loop closed. If cleaning and repasting don't fix overheating, contact the manufacturer instead of trying to refill it yourself.
Custom loops: the coolant maker sets the schedule
This is where a single number stops working. BGR explains the wide 12-to-24-month range by pointing to how much loops and coolants differ: clear fluids, dyed fluids, opaque mixes, metal and plastic parts. Here's what two manufacturers say:
| Product | Manufacturer's replacement guidance | Notes |
|---|---|---|
| Corsair Hydro X custom loops | About every 12 months; every 6 months "if you want to be safe" | Opaque or dyed coolant needs replacing "much more often" to avoid buildup |
| Koolance LIQ-702 | At least every 2–3 years | Replace immediately if color or clarity changes |
Koolance's product listings say its coolants can typically be used for 2–3 years before replacement is recommended, and that you should replace it at least that often, or straight away if the color or clarity changes. Koolance also gives a separate figure, a 3-year shelf life for unopened coolant. That covers storage only and is not the in-loop interval. Its listings also say the warranty doesn't cover third-party coolants, coolant additives or corrosion. So the coolant you choose can affect your warranty, not just your temperatures.
Corsair's Hydro X guide is more cautious. It suggests replacing coolant about once a year, or every six months to be safe, and says that if you don't want to change coolant often, you should avoid opaque or dyed fluids.
BGR names Aquacomputer's DP Ultra and Koolance 702 as the "best of the best." It doesn't cite comparative testing for that, and none was found here. Treat it as an opinion, not a benchmark result.
Section summary: Use the interval printed on your coolant's documentation, not a general rule. Expect clear, long-life coolants to last longer and dyed or opaque fluids to need changing sooner.
What wears coolant out?
BGR lists the usual causes:
- Mixed metals and corrosion. BGR recommends flushing once or twice a year in loops with metal parts. Koolance explains that good coolant includes inhibitors because dissimilar metals and bacterial or algae growth are long-term risks.
- Contamination. Even a closed loop picks up contaminants over time, and how clean the fluid was at the first fill matters.
- Your own handling. Opening the loop more often than needed, or having small leaks, speeds up the decline.
BGR also suggests plastic tubing reduces corrosion concerns. That's partly true, but most loops still include metal blocks and radiators. And neither manufacturer above sets a timetable based on tubing material alone, so don't stretch your interval just because your tubes are acrylic.
Warning signs, and a caveat about temperatures
BGR's list of red flags is sensible: cloudy or murky fluid, visible particles, debris in the reservoir and color changes. For Koolance 702, a change in color or clarity means replace it now. For other coolants, check what that maker says, because the same symptoms can have different causes in different products.
BGR also says that running hotter than usual "typically" means it's time to flush and refill. Be careful with that one. A rise in temperature can come from dust in the radiator, a fan curve that's changed, a pump problem, dried-out thermal paste or a hotter room. Corsair's own overheating checklist starts with dust and paste, not coolant. Use temperatures as a reason to investigate, not as proof the coolant has gone bad.
For both loop types, BGR lists signs of serious failure: unexplained temperature spikes, coolant that stops moving, radiator fans stuck at maximum, and loud pump noise. That's a fair list. Gurgling or rattling in an AIO can sometimes just be trapped air, and Corsair has a separate support article on rattling and bubbling sounds.
A practical routine for custom-loop owners
When you drain and refill, Corsair's Hydro X filling steps make a good baseline. Adjust them for your own hardware:
- Power the system off before you start, because you'll be checking for leaks as you fill.
- Use a fill bottle or funnel to avoid spills, and have a 24-pin jumper ready so you can run the power supply without powering the motherboard.
- Fill the reservoir until it's nearly full, turn on the PSU and watch the coolant move through the tubes. Look for leaks.
- Turn off the PSU before the reservoir runs dry, top it up, and repeat until the level stops dropping when the pump runs.
- Let the loop run for a few hours with the fill port open to bleed out air bubbles, checking for leaks again.
- Stress-test the finished PC. Corsair warns that an overheating loop is more likely to leak.
You'll know the job worked when the reservoir level holds steady, there are no visible bubbles or drips, and stress-test temperatures match what you saw before the refill.
These steps are for custom loops only. They are not instructions for opening a sealed AIO.
The bottom line
The BGR explainer gets the main split right: AIO owners maintain airflow, and custom-loop owners maintain the fluid. Where it oversimplifies is the number. Real-world guidance runs from Corsair's "annually, or every six months to be safe" to Koolance's "at least every two to three years," and dyed or opaque fluids sit at the short end. Find the replacement interval in your coolant's documentation, put it on your maintenance calendar next to dusting the radiator and repasting the CPU, and keep an eye on the reservoir.