D5 Humming

[Toothy1911]

My Alphacool vario D5 pump is over 11 years old. I decided to replace it with a new one, as I was taking it all apart anyway for upgrades / maintenance.
I can't get to the speed adjustment of the vario pump in my current setup, so I got an Alphacool PWM version instead this time (https://www.overclockers.co.uk/alphacool-vpp655-d5-pwm-water-cooling-pump-wc-094-ac.html).
Straight away I noticed the new pump hums a LOT more than the old one. I think there may be something wrong with it. I wanted some opinions before raising a ticket with support.

I run my old vario pump at setting 2-3. Which was 3000rpm and in my system resulted in ~1.3LPH flow.
I've adjusted the speed to 60% on the new PWM pump, to match the 3000rpm. And that's giving me ~1.4LPH at the moment.
Previously I could not hear the pump unless I got right up close to the case, it was "silent". But the new one I can easily hear from across the room. It sends vibrations through my whole desk.
I thought it could be air bubbles, but it's been running for a few hours and the sound hasn't changed. Besides, its too much of a consistent hum to sound like bubbles.

I have not changed the layout of the case at all. It's just been a direct pump swap.

 

[SirConfused]

Is the new pump mounted in the same way and have you tried running it at other speeds? It might just be a resonance issue with the speed of the new one and how it's mounted. Even if it's the same mount, slight differences might lead to resonance if you've only tried a single rpm value. Try at least 10-20% either way, as the flow rate isn't going to change enough to cause concern.

 

[Jay85]

Might sound silly but undo the bolts slightly that hold the pump to the top and see if that helps. It does sounds like resonance and sometimes from my experience releasing it ever so slightly can help reduce it or even get rid of it.

I did this with a DDC lately with great effect.

 

[Toothy1911]

Unfortunately it's noisy throughout its rpm range. Just changes in pitch. It gets no quieter.

I did the retention plate up quite tight, so that's a good idea to back it off a little. I will give that a go. Problem is I have a hard line loop, so I'll have to drain it all to do that haha. Might rig it up on soft line for testing.

 

[Jay85]

Unfortunately it's noisy throughout its rpm range. Just changes in pitch. It gets no quieter.

I did the retention plate up quite tight, so that's a good idea to back it off a little. I will give that a go. Problem is I have a hard line loop, so I'll have to drain it all to do that haha. Might rig it up on soft line for testing.

Also did you use the new or old oring? sometimes the old oring with it being that old will be more compressed than it should be losing some of its vibration absorbing capabilities aka rubber being too squashed and can't reform. If you really cranked it down its more than likely the pump making a solid contact with the top causing vibration/resonance. Backing off should help or change the old oring if you did reuse the old one.

 

[Toothy1911]

Also did you use the new or old oring? sometimes the old oring with it being that old will be more compressed than it should be losing some of its vibration absorbing capabilities aka rubber being too squashed and can't reform. If you really cranked it down its more than likely the pump making a solid contact with the top causing vibration/resonance. Backing off should help or change the old oring if you did reuse the old one.

Should the pump come with an o-ring? I was expecting one to be honest. But there wasn't one in the box. I used the one that came with the reservoir that's about 2-3 years old.

 

[Jay85]

Should the pump come with an o-ring? I was expecting one to be honest. But there wasn't one in the box. I used the one that came with the reservoir that's about 2-3 years old.

Hmmmm good point, it usually comes with the top not the pump.

What did you oring look like? Was it flatter than it should be?

 

[Toothy1911]

I looked like new, and wasn't causing any issues with the previous pump. I'm sure I tightened that pretty well too.
I'll report back later how well reducing the clamping pressure helps. Thank you.

 

[Jokester]

Hmm, yeah if you're using the original o-ring from 11 years ago, it might now be deformed sufficiently to allow the pump internals to be coming into contact with the top itself when you now re-tighten. Personally I would be looking to replace the o-ring with a new one (it that's even available now) or fit a new top.

 

[Mcnumpty2323]

Have had pumps resonate
But never to the point
Of can hear it across the room
And sends vibration through the whole desk
Or through the whole rpm range
Usually change rpm the resonance stops

Only time ever had anything like that
Was with imbalanced impeller

Bit late now
But should have tested it outside the case
Before fitting it
Assuming you have the bits to do it
Especially since got hard tubing

The guys may be right about o ring though

 

[Toothy1911]

Messed about with it this afternoon. Thanks for the input so far gents.
The o-ring is fine. It's only 2-3 years old. This pump has had a few different tops / reservoirs over the years.
I tried loosening the clamping plate for the pump. Didn't make a difference.
I then tried my old impeller in the new pump, still no difference.
I tried the new impeller in my old pump - and it was silent. Like before. So I think the impeller is balanced, as this was my main thought too.
Tried PWM control from both my Aqua Computer Quadro and the motherboard header, no difference.
I added some rubber dampening to the pump mounting, which made next to no difference.
The vario pump will cause some vibration to start resonating when it's turned up (I tried it at 4). Not as bad as the PWM though.

Conclusion. Motor, spindle and the fact it's PWM controlled are the only differences. The motor isn't a moving part, so unless there's something wrong with it's windings, I can't see why that would be causing the hum. Ceramic bearing on the shaft could be at fault, but I have no experience of the failure modes. Do they squeal, rattle, hum when the bearing is bad? No idea. I've done some reading and some people say the PWM control introduces noise and others flat out reject that and say there's no difference.

I have re-installed my old pump and will look to send this one back as faulty. Maybe I'll get another 11 years out of it yet

 

[Mcnumpty2323]

Can't say pwm control
Makes mine noisy
At a certain rpm there was a bit of resonance
But above or below that rpm
It went away
Bit of a strange one but you've tried what you can
Send back as faulty is about only option
Left to you

 

[SirConfused]

You've tried all the sensible stuff, the only reasonable conclusion you can come to is that it's some sort of faulty. Are you looking for a replacement or just going to get a return and live with your old pump?

 

[Mcnumpty2323]

@Toothy1911
Should mention just in case it's useful
@davido_labido has a load of watercooling gear
For sale in MM
Pretty sure he had some pumps in there

I also have a d5 pump/res combo in MM
Though wouldn't sell the d5 separately

 

[Toothy1911]

You've tried all the sensible stuff, the only reasonable conclusion you can come to is that it's some sort of faulty. Are you looking for a replacement or just going to get a return and live with your old pump?

Think I'd just take a refund if they offer it me. It's such a pain to pull my system apart to change it. I was only changing it because I was fitting some spacers to line up my hard lines, for my new motherboard.
I also risk going through the bother and the replacement pump giving me the same problem, a bit pessimistic I suppose, but I've not had the best luck so far!

@Toothy1911
Should mention just in case it's useful
@davido_labido has a load of watercooling gear
For sale in MM
Pretty sure he had some pumps in there

I also have a d5 pump/res combo in MM
Though wouldn't sell the d5 separately

Thank you. I went and checked the adverts. I think I will leave it for now, as above. Maybe I'll look into it again next time I need to drain and change the loop. GPU upgrade or something. Appreciate the help guys.

I submitted a support request last night, just waiting to hear back.

 

[Jay85]

Think I'd just take a refund if they offer it me. It's such a pain to pull my system apart to change it. I was only changing it because I was fitting some spacers to line up my hard lines, for my new motherboard.
I also risk going through the bother and the replacement pump giving me the same problem, a bit pessimistic I suppose, but I've not had the best luck so far!


Thank you. I went and checked the adverts. I think I will leave it for now, as above. Maybe I'll look into it again next time I need to drain and change the loop. GPU upgrade or something. Appreciate the help guys.

I submitted a support request last night, just waiting to hear back.

Its really hard to tell but i suppose if the ceramic bearing was even slightly off or mishaped it could cause the hum. Return and get something else tbh, maybe look for an older XSPC D5, all the ones i had back then from XSPC were rock solid. EK ones however were abit hit and miss.

 

[Toothy1911]

Still waiting for a response from customer service after 4 days I hope this isn't going to be a big pain in the bottom.

 

[Mcnumpty2323]

Still waiting for a response from customer service after 4 days I hope this isn't going to be a big pain in the bottom.

How did you contact them?
Last time I sent a Web note to them
It took literally 7 minutes to get a reply

 

[Toothy1911]

How did you contact them?
Last time I sent a Web note to them
It took literally 7 minutes to get a reply

Via the web ticket system

https://help.overclockers.co.uk/hc/en-gb

 

[Mcnumpty2323]

Via the web ticket system

https://help.overclockers.co.uk/hc/en-gb

If they hadn't replied within 1 day
I would phone them