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How to Repair a G5 Quad Dual Pump LCS

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Thank you @BadGoldEagle

Anyway I saw the screws have a "limit” (you cannot tighten them in infinite) and that’s the reason why I asked. I’m thinking maybe they were not tighten enough.


About the o-rings... yeah but the pressure is between the copper and the little aluminum plate. Which is "unusual”? Strange anyway. But I’m thinking LOL if they were put there for assembly only.

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8 hours ago, mePy2 said:

Mhm... yeah... are you sure about it? And then, why putting them at all?

(I found they are useless too. I mean, I cannot see their functionality)


Another thing, when putting the screws with the springs (the one that attach the CPU PCB to that metal plate behind the copper liquid thing) should I tighten them until the screws stop? 

I didn't say they had no use, I said it helps assembly when attaching the waterblock to the CPU.

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Just sent the same post two times... apparently I cannot delete it...


Since I am here... would someone explain me “what I have done” in the picture above? It was not me, but the old owner. I do not like it though. I am worried since it is the CPU PCB itself.

On 11/12/2019 at 2:00 PM, mePy2 said:

Guys, another thing... what can I do for these?



do you suggest me to change the thermal compound on the North Bridge too? How can I check its temperature?


Edited by mePy2
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  • 3 weeks later...

Hello again... I wrote a long post until the page refreshed. I’m very frustrated now...
Anyway I made the disassembling.
What I have now is this:
• the liquid was like water, no color at all...
• there was little liquid inside
• no @BadGoldEagle orange little balls
• what kind of hoses they are? Seems very strong and made with two materials. The inside is something like plastic, and outside rubber.
• What kind of glue it is? I need the same glue.

That’s all... :)

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  • 1 year later...
On 11/15/2019 at 2:41 PM, mePy2 said:

@kby You wrote about testing the LCS connecting it directly to its wire. What about those holes in the CPUs PCBs? I mean they are always power related... I do not want to make something wrong. Thanks

Sorry; not on here a lot. Presumably you have figured this out, but those are the connectors to power the CPU. They won't power the pump. You won't even have the CPU cards attached to the system to do the heat gun/hair dryer test.

The glue appears to be a thermal glue. I have not messed with the glue down by the blocks. I have had some on the pump connections that had to be replaced to removed the hoses; I replaced it with some organic-based (toluene solvent) flexible stuff; usually goes by the name "Goop"

(I know, really specific, but that is the trademarked name it is sold by). The old stuff will chip away fairly easily. It appears to be hot glue gun glue to me, but I don't know for sure. I have never pulled out the CPU blocks. If it ain't broke, don't fix it.


You can think of the assembled system as a sandwich for each CPU where the top piece of bread is the CPU and the bottom one is alumnium plate. The inside of the sandwich is the CPU cooling block. THe spring-loaded screws that go through hold two pieces of bread together tightly around the filling.


I don't prefer automotive coolants as they are toxic (not that we should be drinking them here anyway and shouldn't really be needed. The CPUs will shut down around 80ºC so the coolant doesn't get that close to the boiling point of 100ºC. Combustion temperatures in an automotive engine are much higher (~230 ºC) which is much higher than the normal boiling point of water. Such systems in addition run significantly pressurized. LCS for computers generally run pretty close to atmospheric.


The corrosion inhibitors in traditional antifreeze are probably more atuned to protecting iron rather than alumnium, although these days most include some aluminum corrosion inhibitors. Again, you're not dealing with all the ugly byproducts of closed combustion, so this is kind of a moot point for a computer LCS.


I would not worry about the look of the CPU board connects. They are bolted down with a star washer than bites into the surface, so they'll always look a bit ragged. Worry if there's no metal or the metal is coming off.


Commenting on the original poster's pictures, I have had bad luck with tygon (transparent vinyl) tubing. It looks good and I would normally think it would hold up better, but in practice it didn't. It leaks more as it gets soft at the upper end of the temperature range.

You can't clamp it down as tightly either, as it deforms and/or perferates.-kby



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  • 4 weeks later...

Hi all,


I've a never serviced before Quad G5 - single pump revision 1 "Delphi" unit.  It's been a long time since I fired it up, I recall it ran OK but best with the G5 laying on it's side, which to me suggested low coolant.


I've pulled the water cooling unit, and can hear coolant sloshing around inside.  It is not leaking - there is no evidence of any wear or corrosion, it is spotless.  It may have been an Apple recalled unit?  To avoid complete disassembly I'm tempted just to clamp on some longer tubing and flush the coolant, or at least see what comes out.  Repasting the CPU might also be a good move during this process.  I've a spare Laing D5 pump (12V from PC watercooling days) that might help here.


- Are there any filters in the tubing to check - if so, where?


- Does the internal of the CPU block "maze" get significantly clogged - or do you reckon I just leave it be?





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There were two in mine. As I recall -- it's been quite a few years -- they were at points where liquid flows into the radiator. I have, however, removed those filters (they were pretty solidly clogged when I went at it) and replaced them with a single small in-line automotive fuel filter before the pump, which will be much easier to service when the time comes, and it seems to me much more forgiving just because of the physical size of the filtering. (To access those two small filters, btw, I had to cut away tubing with a utility knife, clean off sealant, etc.)


Yes, the mazes get clogged, noticeably. At one stage I went so far as to remove the mazes as an experiment because they are a failure point (did not go terribly well, the mazes matter, though the machine did run okay-ish without them). Once the thing is apart, however, the mazes are easily dealt with, as it is all just compression via screws around O rings, so I would not worry about that end of the matter. The most difficult thing is getting the radiator properly refilled. That can probably most easily be started once the mazes are exposed, through the open circuit at the heatsinks. All the same, it is impossible to get the air out at the initial stages of the refill, largely because so much gets trapped in the fins of the radiator, in the pump, and so on, and because you are dealing with airlocks in the system.


To deal with that problem, I installed a capped length of hose at the high point on my circuit, coming from a T junction, which allows me to get air out and more coolant in (I use a syringe) once the thing is running. On initial startup, you get a great deal of foaming in the system, but if the air bubbles have a way to get out, get out they will. My high-point T-junction solution does that job pretty well; the bubbles release air as they pass and it comes up the tube. It takes a couple of hours for the system to clear of all air after a refill in this way.


That sloshing in yours suggests strongly that the system is only partly full, but the greater problem is more likely to be sediments in the filters/maze and dated heatsink compound. I don't think the liquid ever gets very warm, so low levels should not be the main factor. Just my opinion, mind.


I've had mine apart now something like three or four times. I think I'll soon have it down to a fine art.

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@beachycove Thanks for the additional info, much appreciated.  Agree that the sloshing may not just indicate low coolant; I'll be interested in seeing what crud comes out.


Sounds like it's a case of "do it properly" then make some minor improvements in tubing, coolants and double check all so that when servicing is required in a couple of years it won't be as arduous.  Obviously wasn't hoping for that and was feeling lazy :)





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