How is it possible for air bubbles to form in an AIO pump which has been working without this issue for 3+ years?

[em4n3m]

Hi all,

 

After 3+ years using my Arctic Liquid Freezer II, suddenly, I have noticed some air bubbles in the pump of the unit - producing a very loud and unmistakeable gurgling noise, typical of the same.

I tilted my case and, eventually, the bubble noises went away. Nonetheless I bought a new AIO (same make/model), can't risk to have anything broken, especially a potential water leak.

After installing the new AIO, have been running 

stress --cpu 32

(on Linux) on my 5950x for 40+ minutes and the temps have been stable at 67C.

 

The radiator is (and has been) mounted horizontally on the top of the case, and the CPU pump is way below it, hence I can't quite understand how air bubbles formed/reached the pump if the case hasn't been substantially moved for years (apart slightly moving for cleaning the floor). Also, the pump fan on my motherboard has been set to 'max speed' since ever, no changes there.

What could have been the reason for air entering the closed loop and getting to the pump after 3+ years of sustained use (10+ hours/day average)?

I haven't had air in the pump since day one, and now all of sudden I had loads of it (the gurgling noise was really loud)?

Got really scared and decided to replace it, even if I was able to have the air move 'up' in the radiator.

 

Thanks!

[Average Nerd]

Most likely reason is that a seal failed and coolant started evaporating, eventually the amount of air got large enough to get sucked into the pump.

 

[Stahlmann]

It's completely normal for any water cooler to have some air in the loop after multiple years of use. Even though my open loop doesn't leak, there are about 100 ml of water "missing" from the reservoir 3 years later. Contrary to popular belief, my system is still running fine 3 years after the initial setup with no maintenance whatsoever and temps are still the same. I'll probably only do maintenance when i finally replace the GPU in 2 or 3 years, at which point it's (hopefully) been running for over 5 years.

 

The same thing happens to AiOs.

 

If the air is in the pump, make sure the pump isn't the highest point of the loop. If it isn't, rock the PC around a bit while it's running and the air should make it's way to the highest point, which ideally should be the reservoir or a radiator.

 

A few AiOs also support refilling the "lost" water.

[Agall]

28 minutes ago, em4n3m said:

Hi all,

 

After 3+ years using my Arctic Liquid Freezer II, suddenly, I have noticed some air bubbles in the pump of the unit - producing a very loud and unmistakeable gurgling noise, typical of the same

Technical term is cavitation. Not good for pumps since it can result in overheating.

 

AIOs will have slight evaporation over time, so 3 years later, you'll have less fluid in the loop than when you first got it.

 

Getting the bubbles out of the pump is a good idea. If it happens again, I would investigate why they're collecting in the pump which should be a low point. Unless you're using a 'no no' configuration, it shouldn't happen unless there's a leak point in the pump itself.

 

 

[em4n3m]

5 hours ago, Average Nerd said:

Most likely reason is that a seal failed and coolant started evaporating, eventually the amount of air got large enough to get sucked into the pump.

 

Thanks, this seems the most plausible explanation so far on why it did happen after 3+ years of running fine.

Before I mark as solution, any commentary on changing the AIO? I.e. is a good thing if one can't refill the liquid?

[Average Nerd]

2 minutes ago, em4n3m said:

I.e. is a good thing if one can't refill the liquid?

Some AIOs have fill ports, others don't. It really depends on how much effort the manufacturer puts into their product.

[em4n3m]

Just now, Average Nerd said:

Some AIOs have fill ports, others don't. It really depends on how much effort the manufacturer puts into their product.

Right, so if one can't /isn't able to, should the AIO be replaced then a safety measure?

[Average Nerd]

6 minutes ago, em4n3m said:

Right, so if one can't /isn't able to, should the AIO be replaced then a safety measure?

If it still works, you can of course still run it until it dies, since the CPU has overtemperature protections that will throttle it down or force your PC to shut down if the CPU overheats.

If you don't want to risk anything, you can replace it.

[TatamiMatt]

6 hours ago, Agall said:

Technical term is cavitation. 

Wait really? AIO pumps can move fast enough to cavitate? Wild

[Agall]

8 minutes ago, TatamiMatt said:

Wait really? AIO pumps can move fast enough to cavitate? Wild

The same concept applies in a simplistic form. Either by insufficient head pressure or air in the pump in this context.

[freeagent]

Permeation.. coolant evaporates, custom loop guys top up, AIO guys.. break their warranty if they try to top it up

 

Run till done..

[TatamiMatt]

8 hours ago, Agall said:

The same concept applies in a simplistic form. Either by insufficient head pressure or air in the pump in this context.

Ah okay not cavitation in true sense? Where it implodes and vaporises liquid due to pressure? Or does it actually do this, if so those little pumps are much stronger than i initially thought (ive never owned an AIO)

[Stahlmann]

11 hours ago, em4n3m said:

Thanks, this seems the most plausible explanation so far on why it did happen after 3+ years of running fine.

Before I mark as solution, any commentary on changing the AIO? I.e. is a good thing if one can't refill the liquid?

As long as it doesn't keep happening all the time, get the air out of the pump and continue using the AiO like you did before. Most AiOs cannot be refilled, and the ones that can be are typically more expensive. It's your decision when buying an AiO whether you want to pay for that or not.

[Agall]

7 hours ago, TatamiMatt said:

Ah okay not cavitation in true sense? Where it implodes and vaporises liquid due to pressure? Or does it actually do this, if so those little pumps are much stronger than i initially thought (ive never owned an AIO)

Don't be daft, you're taking the industrial form of a definition that obviously doesn't apply. Cavitation has been used to describe a similar effect that happens when there's insufficient head pressure or air stuck in the pump and there's excessive noise in the pump from it.

 

15 hours ago, Agall said:

The same concept applies in a simplistic form. Either by insufficient head pressure or air in the pump in this context.

I'll put this back here so you can actually read it this time.

[TatamiMatt]

7 minutes ago, Agall said:

Don't be daft, you're taking the industrial form of a definition that obviously doesn't apply. Cavitation has been used to describe a similar effect that happens when there's insufficient head pressure or air stuck in the pump and there's excessive noise in the pump from it.

 

I'll put this back here so you can actually read it this time.

Apologies, ive never heard it used in that term before, i work in the engineering industry, I've only ever heard it in the industrial sense

[Agall]

2 hours ago, TatamiMatt said:

Apologies, ive never heard it used in that term before, i work in the engineering industry, I've only ever heard it in the industrial sense

I've seen real cavitation in a couple different scenarios since I've operated nuclear reactors and was a main engine operator on an aircraft carrier that controls the propellers. You could feel/hear it, depending on where you were on the ship with the propellers, the latter like the feed pumps to the steam generators or other fluid systems would almost never cavitate (good operators and procedure). If the reactor coolant pumps ever cavitated enough to notice audibly or visibly on instruments, that would be a really bad time since its heavily subcooled in that part of the loop which also affects reactivity heavily.

 

Simplistically, its the same in practice, being that there's low pressure pockets at the impeller that's impeding its function, indicated by excessive noise, caused by air or low head pressure/height.

 

Something like an AIO isn't high energy enough to reach saturation conditions to meet the more extreme form of the definition. It would have to be drawing in excess of 5lbs or so of vacuum to do that at STP, assuming ~60C (been a while since I stared at those charts), which I don't think a standard loop could handle. Years ago, I theorized about running a loop at saturation with water, really its just not practical since you'd have to draw a vacuum, let alone the chemistry involved, but its been a while since I've thought about it.

[RevGAM]

On 1/15/2024 at 4:26 PM, em4n3m said:

Thanks, this seems the most plausible explanation so far on why it did happen after 3+ years of running fine.

Before I mark as solution, any commentary on changing the AIO? I.e. is a good thing if one can't refill the liquid?

I'm going to disagree with @Average Nerd. The most likely reason is what @Agall said, and/ or evaporation through the tubes due to osmosis/permeation. The time it takes depends on the material used for the tubes. My understanding is that the harder the tubes, the slower. 

 

Cavitation is when there is a sudden pressure change that results in gas forming. That gas is one reason why your joints can be cracked (another is damaged cartilage).

[Average Nerd]

@RevGAM yeah, I only realized that osmosis was a thing after someone else had already said it.

[Agall]

1 hour ago, RevGAM said:

I'm going to disagree with @Average Nerd. The most likely reason is what @Agall said, and/ or evaporation through the tubes due to osmosis/permeation. The time it takes depends on the material used for the tubes. My understanding is that the harder the tubes, the slower. 

 

Cavitation is when there is a sudden pressure change that results in gas forming. That gas is one reason why your joints can be cracked (another is damaged cartilage).

The phenomenon itself can be quite complex since its possible for this effect to occur from a local drop in gas solubility that can build up in the pump, so not even just vaporization from operating near saturation.

 

Apparently the technical differences is vaporous cavitation versus gaseous cavitation. I've also seen it called air entrapment and not cavitation, but this is where using specific definitions isn't always the best.

 

Depending on the program or specific instructor/professor will vary on how something is defined, which is why detailing definitions is always important. In the context of computers and water cooling, cavitation is a common definition for what we're all discussing.

 

28 minutes ago, Average Nerd said:

@RevGAM yeah, I only realized that osmosis was a thing after someone else had already said it.

Almost nothing is 100% sealed, there's usually at least some chemical or mechanical way that things get in or material gets out of any fluid system. Permeability of the tubing being one, where AIO manufacturers have to balance elasticity with permeability, as well as other variables. Eventually any AIO will lose enough fluid or become fouled enough to require service/replacement.

 

I haven't heard of situations where heatpipes experience the same problem, since those are technically fluid systems, but they're rigid unlike the flexible tubing of AIOs, and there's really no marketable way that an AIO could use rigid tubing.

 

The only way I can think of is a case that comes with an AIO and the radiator is top mounted. Then the case is designed with tolerance in the X,Y,Z for the radiator mount that involves spacers that would allow the user to mount the AIO pump on the CPU and then compensate for the rigid tubing by adjusting radiator positioning. Potentially a system like EVGA's recent gucci case with the tensioning system, having the radiator floated with this that would allow rigid tubing. Overall, likely not worth the design constraints.

[RevGAM]

1 hour ago, Agall said:

The phenomenon itself can be quite complex since its possible for this effect to occur from a local drop in gas solubility that can build up in the pump, so not even just vaporization from operating near saturation.

 

Apparently the technical differences is vaporous cavitation versus gaseous cavitation. I've also seen it called air entrapment and not cavitation, but this is where using specific definitions isn't always the best.

 

Depending on the program or specific instructor/professor will vary on how something is defined, which is why detailing definitions is always important. In the context of computers and water cooling, cavitation is a common definition for what we're all discussing.

 

Almost nothing is 100% sealed, there's usually at least some chemical or mechanical way that things get in or material gets out of any fluid system. Permeability of the tubing being one, where AIO manufacturers have to balance elasticity with permeability, as well as other variables. Eventually any AIO will lose enough fluid or become fouled enough to require service/replacement.

 

I haven't heard of situations where heatpipes experience the same problem, since those are technically fluid systems, but they're rigid unlike the flexible tubing of AIOs, and there's really no marketable way that an AIO could use rigid tubing.

 

The only way I can think of is a case that comes with an AIO and the radiator is top mounted. Then the case is designed with tolerance in the X,Y,Z for the radiator mount that involves spacers that would allow the user to mount the AIO pump on the CPU and then compensate for the rigid tubing by adjusting radiator positioning. Potentially a system like EVGA's recent gucci case with the tensioning system, having the radiator floated with this that would allow rigid tubing. Overall, likely not worth the design constraints.

Are you aware of which types of tubing are less permeable?

[Agall]

18 minutes ago, RevGAM said:

Are you aware of which types of tubing are less permeable?

I don't remember off the top of my head, but I've seen discussions about there being two major types, one of which is more permeable and the other is less flexible.  Might take me a while to find that discussion again, wasn't on these forums but I think from a GN video.

[BahnStormer]

Some air leakage is inevitable. I think there are hardline and some flexible lines that less porous than others, plus custom loops (i.e. with reservoirs) will handle this better than a closed loop AIO.

 

@OP - Fantastic to hear that your Artic Freezer lasted 3 years - my previous Corsair AIO's lasted 3 to 18 months each before they failed (one pump failure at 3 months and 2x had too much air after 15 months and 18 months). After that, I went over to a Noctua NH-D15.... back on AIO now, but Artic Freezer II.

[RevGAM]

7 minutes ago, BahnStormer said:

Some air leakage is inevitable. I think there are hardline and some flexible lines that less porous than others, plus custom loops (i.e. with reservoirs) will handle this better than a closed loop AIO.

 

@OP - Fantastic to hear that your Artic Freezer lasted 3 years - my previous Corsair AIO's lasted 3 to 18 months each before they failed (one pump failure at 3 months and 2x had too much air after 15 months and 18 months). After that, I went over to a Noctua NH-D15.... back on AIO now, but Artic Freezer II.

I must remember never to get a Corsair AIO.  

[freeagent]

4 hours ago, RevGAM said:

I must remember never to get a Corsair AIO.  

I have an empty one you can have

[RevGAM]

On 1/18/2024 at 12:30 PM, freeagent said:

I have an empty one you can have

Send it on over with those old TR air coolers you no longer want.