A few drops of high quality lubricant

[Muse]

I have a couple of 200mm computer fans mounted in my bedroom window. Been there close to 10 years, I guess. During warmer weather I flip on a switch that's mounted to my bed stand. It cools the room maybe 5 F degrees. I also have a window air conditioner mounted in that window, but rarely turn it on. It's noisy as hell and, of course, expensive to run. I only turn it on for a few minutes in extreme heat situations, maybe once a year.

Now, the computer fans I have powered by a wall wart. Draws very little current, is near free to run and close to silent. I can hear the fans but it's a gentle whoosh, nothing problematical. However, occasionally, lately, they develop an eccentric relatively intense noise, and I think it's because the lubrication in the fans has gone bad or evaporated. I think it's also alleviated (stopped) when the fans bearing gets warmer. So when it does that, I let them run a few seconds and turn them off and on again. Doing this a time or two eliminates the eccentric spinning and they run quiet again.

Now, I've opened them up a time or two and replenished the lubrication in the bearings. I used the best lube I had, and some research suggested that for this purpose a full synthetic transmission fluid was the best to use. I'd had my transmission fluid in my '97 Mazda sedan changed about 10 years ago and had an almost empty bottle of expensive fluid and used a few drops of that to lube the computer fans. But the bottle is virtually dry now, there's maybe a drop in there and I don't think I should use that, the volatile fluid in it has probably evaporated significantly.

A single quart of Red Line All-Synthetic formula tranny fluid (it's what I had put in my Mazda) is over $20. Seems silly to spend that when I only need 1 ml of fluid. I have various other lubricants. What would be a good lubricant for this purpose. Of course, it should not only keep the fans smooth and silent, it should last for many years so I don't have to disassemble the fans again any time soon.

 

[Paperdoc]

My first thought was: How can you do that? Most current computer fan designs are such that you cannot disassemble them enough to gain access to the fan bearings without damaging the chassis so badly it cannot be re-assembled. And of course, merely forcing oil into a fan without being able to direct it only to the bearings means you will foul the entire fan insides with oil.

However, you appear to have succeeded so far. For such small fans I have never searched for special high-performance oils. I simply use a light oil I have for sewing machines. It has lower viscosity than most machine oils, and that is right for a device with low rotational speed and little mechanical weight to support.

For background, you should consider this a symptom of long-term bearing wear, NOT just lack of lubricant. As a fan ages its bearings wear so that the sleeve hole diameter increases slowly. A related factor is thermal expansion: the sleeve material expands less than the shaft material as temperature rises. So with worn bearings at cold (room) temperature, there is too much clearance between shaft and sleeve and the fan rotor "rattles" in the sleeve when it starts up cold. As it runs the sleeve expands less and the clearance shrinks until it can run smoothly. Stop and re-start that fan while still warmed up and it stays silent. But stop for a long time to cool down and the process will repeat. As time goes on and wear increases, this noisy start-up behaviour lasts for longer times, until it becomes almost permanent. If left alone for longer, eventually it will result in the fan's seizing up and stopping. By adding oil to the bearings you can delay this process by "filling" the expanded clearance with lots of oil, but you cannot stop the long-term wear process. Solving this means replacing the fan eventually.

 

[Muse]

The fans are Cooler Master A20030-07CB-3MN-F1

12V 0.30Amp

They have a sticker on the center that is around 2 3/8" in diameter and I pulled them back and placed the lubricant in there and IIRC it was (I thought) where it would get right into where the bearing would receive it beneficially. Seemed to do the trick when I did it but it's been several years so my memory is really nothing more than what I said here... peel label back, insert the lubricant and press the label back on.

I could try sewing machine oil, I have lots of it (have a ~70-80 year old Singer sewing machine, 403A IIRC), but it's not Singer oil, it's some third party. It looks perfectly clear.

The sticker is on the side towards which the air flows, so it's easily accessed from it's mounted position. Therefore pulling up the stickers, etc. does not necessitate unmounting the fan. I can do the whole thing just kneeling on my bed.

I also have almost a quart of transmission fluid, but it's not full synthetic.

 

[mindless1]

Ball bearing fans, almost always have sealed bearings so you can try pressing the old bearing out to replace it but might destroy the plastic.

It's the viscosity and how you achieve it, rather than how "high quality" relevant to some other lubrication application, that matters.
By how you achieve it, I mean you want a light oil but that is thickened, so that base oil penetrates the bushing, but is held in place by the solids thickening it too. This serves as a faux-reservoir, see more below.

Sleeve bearing fans, there are two options, most people end with the the second situation.

1) Either you relube the fan before it runs dry and wears the bearing, using a light oil (5w20 motor oil would be fine) continuing to do so on a schedule before it shows any signs of a problem, OR

2) Once you have an elliptical wear in the bearing, you have to switch to a more viscous lube. This reduces the elliptical wobble, and pumps out of the bearing less. The thinner oil (in the mix described below, instead of just using a very viscous oil like gear lube) will weep out and seep into the porous bushing more.

Another alternative more often found on larger fans is there is a felt/etc-material on the end of the bushing to hold a reservoir of thinner lube, light oil but again once the busing is worn, it needs a thicker lube. Adding a custom cut size piece of felt to help improve the reservoir holding capacity would help, but may not be needed, depends on amount of wear. If we want to get to the ultimate answer then it's replace the fans and lube them more often.

The lube does not have to be extra-special *quality*. I just use motor oil mixed with moly-free NLGI #2 lithium grease, mixed to a viscosity with a drop point barely above room temperature. I mixed up a batch in a pill bottle, and put some in a little squirt bottle as well, and it's more or less a lifetime supply for the small amount needed for (relatively speaking in the realm of fans, very small...) computer fans.

Pack the bushing cavity nearly full with it, and if the sticker has the adhesive shot because the prior lube got into it, you'll need to thoroughly clean the area and put a new sticker on. It can be a piece of tape, or a plastic mailing label, just not uncoated paper. This matters less to not at all if it has a high quality rubber bung seal that does its job, seals completely.

Hold the fan hub/blades in towards the bushing and as the rubber plug is put back in, let the pressurization from that, push the fan hub/blades back out. It's easier to do than describe, you're reducing the amount of air displacement happening. The other option is put a bit less of the mix in the bushing cavity and pack the back of the rubber plug with it and still do the same displacement procedure.

Full synthetic oil mixed with synthetic (or not) grease would be fine but is not needed, synthetic has virtually no benefit in this application.

No matter what you use, once you have worn the bushing, you may find you need to relube it every 10,000 hours or so, or more often the more wear that has already occurred.

Heh, I wish I could have condensed the above into fewer sentences but there are several variables. Just telling you what has worked very well for me, for decades on all types of sleeve bearing fans and other motors, including a lot of computer fans. At the same time there is a point of no return where it's just not worth the bother as the wear is too great, the relube interval too short, to not just replace the fans.

 

[Paperdoc]

On a lot of modern fans there is no sticker on the hub of the blade assembly - it's just a solid moulded hub. But even for those that have a sticker, what is exposed under that usually is just the end of the rotor shaft that has the moulded blade part press-fit on. Effectively that established a seal between shaft and moulding, so oil cannot flow past that to reach the bearing at that "front" end of the shaft. To reach that bearing you need to be able to pull the blade unit off the end of the shaft, then replace it when done. For many designs that is extremely difficult without damaging the blade unit (potentially making it unbalanced) or the motor chassis so that you can't re-assemble.

BUT there also is a "rear" bearing normally press-fit into the moulded back part of the motor chassis, and there is almost never any opening, blocked off by sticker or open, where you can add oil there. On much older fans the motor chassis was in two halves held together with removable devices like screws or snap-tabs, and you could separate those to disassemble and remove the rotor / shaft unit and access the rear bearing. This usually was the easiest way to access the front bearing, too. But today's fan designs appear to fasten the two chassis halves together permanently with adhesives or ultrasonic "welding" so you can't do this.

 

[mindless1]

^ This is a reason why I don't want this crappy newer fan design, meant to shave a few cents off the BOM then it can't be serviced the same.

However I am not clear on what you mean by "established a seals.. so oil cannot flow past that to reach the bearing at that "front" end of the shaft.

In PC fans, the bushing is practically always a single piece, where if you get lube to one end, it will transfer to the other end. It's not sealed off because of wear if nothing else. This is entirely different than larger motors with separate bearing at each end, or dual ball bearing PC fans.

I haven't seen any PC fan that I couldn't lube, even if it meant that I needed a hot needle to melt a hole to gain access, then just use a razor blade to trim any molten plastic off that extended past the outer plane of the area of attack, then seal that with tape or RTV, etc. This is only true of sleeve bearing fans. The worst type of fan has one sleeve and one ball bearing. Coolermaster among others a long time ago, were notorious for that crappy design, especially on sub-25mm thick fans where the thinner diameter meant higher RPM necessary so they burnt through their lube all that much faster.

This brings me back to a central issue, which type of fan to choose. For the ultra-silent PC crowd it's sleeve bearing, but one with a fancy name for the bearing, but I've always gravitated towards dual ball bearing fans instead, because they may make a little more noise when new, but once they get excessive wear, still tend to run for many thousands of hours longer before complete failure. I don't even recall having a major brand dual ball bearing fan that ran below 3000RPM, ever failing. By major brand I mean a fan manufacturer such as Sunon, NMB, Panasonic, Nidec, Papst, Delta, Comair, etc., not a wider scale PC component relabeler like Coolermaster, Antec, etc.

Anyway, I'm not a nut about what has the absolute lowest free air rated noise, since it is usually the surrounding components that cause the turbulent noise, so I'm very much a fan (pun intended) of just getting the major brand sleeve bearing fans (if you want sleeve bearing) from electronics surplus sites then relubing them before their first deployment. Doing this I have never had a fan fail, but again I mostly pick dual ball bearing when circumstances align and I see the size I want at the right price at the time.

Wow I wrote a lot and should have backtracked a bit to look at the topic in context. There are real window fan assemblies available. It's a solid option, and I happen to have one running right now. I got the following at a great discount as an amazon warehouse item:

https://www.amazon.com/gp/product/B000065DK8?psc=1

... think it was $28 at the time, and as soon as I received it, I opened it up and put more lube in. Only complaint is that if set to the lower speed, it creates a hum so I keep it on high speed. Well I do have a 2nd complaint which is that it is too smart, to the extent that if I have a power outage it reverts to off when I'd rather it just started back up when power was restored.

 

[BoomerD]

I have a couple of old CoolerMaster 230mm fans (HAF932 case) that I've brought back from "fan death" with the addition of a couple of drops of CorrosionX. Peel off the sticker, remove the rubber plug, give it just a couple of drops of the lubricant, wipe it carefully, reinstall the rubber plug, tape the sticker back in place...good to go for another year or so.