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Quad G5 Liquid Cooling System overhaul help

So, since my Lenovo Core 2 Duo died (worthless computer..), I've been without a laptop. This also means I'm using my Beige G3 for all my internet and computing needs.


I suppose that might be fine if everything out there (the internet included, and perhaps especially) weren't horribly-programmed bloatware.


Anyway, a few months ago I got a Quad G5 off eBay for $150, As-Is. What turned out to be wrong with it is that the LCS needs to be overhauled; unless I run it in "Reduced" mode in Energy Saver, it crashes within ten to fifteen seconds of use at full speed, after hitting over 200F.


Only problem is, I"m not quite sure what tools I need.


It's a Quad G5, with the Delphi LCS block. Can anyone link me to EXACTLY what tools I need to take the thing apart? I know I need some sort of Hex screws and torx screws, but do NOT know what size. I know I need O-Rings, but don't know how to meausre them exactly, so I don't know what size I'd need. I *DO* know what kind of coolant to use... I don't really know what sort of tubing to buy.


Please help? I really like the Quad, it's very fast... and that's at literally 1/2 speed. But I certainly can't justify upgrading it yet without being able to use it at 2.5 GHz instead of 1.25.


Help is much appreciated. Again, what I need is the specs of tools I need, quite preferably links to exactly what I need. I know XLR8YourMac etc. have done a lot of detailed guides on this, but they weren't on Quad G5s, and AFAIK the tools necessary are slightly different for a Quad. Thanks!

PowerMac, Mac OS X (10.5.8), Quad G5, 1.5 GB RAM, 750 GB, 7800GT

Posted on Oct 3, 2011 8:32 AM

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50 replies

Oct 5, 2011 12:02 AM in response to Dan-Lempesis-Omega

In addition to the tools listed in the service manual (scribd link above), you need a 2,5mm hex driver to take the CPU modules off the LCS assembly. If you don't break the tubing, you shouldn't need to buy any. If the CPU blocks aren't leaking, I don't see the need for new O-rings, either. O-rings for the pump, if required, are available from most places selling PC water cooling stuff. A 12VDC 1.8A power source (even better if adjustable) will be handy for powering the pump outside the case.


New thermal grease will be needed if you detach the CPU modules. I would use Shin-etsu, either G751 or X23-7783D; I've seen no degradation in performance compared to the original grease when using X23-7783D. No idea what thermal grease they used at the factory, but it looks similar to the Shin-etsus. I'd suggest "blob in the middle" application method.

Oct 5, 2011 8:38 AM in response to Heikki Lindholm

Hm. If the tubing *does* break (=P it might, I think the fluid might be dried up in there...) what should I use?


As far as thermal paste goes, all I've got is Arctic Silver. Any chance that'd suffice? =P

I don't think I really want to power the pump outside the computer... what would I do that for? To test it/clean it..? I've never done this before....


Blob in the middle works for me 🙂


Thanks so much for the replies by the way.

Oct 5, 2011 12:15 PM in response to Dan-Lempesis-Omega

Dan Lempesis (Omega) wrote:


Hm. If the tubing *does* break (=P it might, I think the fluid might be dried up in there...) what should I use?


As far as thermal paste goes, all I've got is Arctic Silver. Any chance that'd suffice? =P

I don't think I really want to power the pump outside the computer... what would I do that for? To test it/clean it..? I've never done this before....


Blob in the middle works for me 🙂


Thanks so much for the replies by the way.


For the tubing, I would go to some industrial supplier and get some reinforced tubing suitable for water cooling (ie. ethylene or propylene glycol compatible). I think the tubing needs to be 3/8 ID, that's what the pump barbs are. Opaque tubing is probably better in not harboring life in there 😝


Arctic Silver might work, but imho it's too runny and conductive for the job, and it also doesn't match current greases performance-wise. Use AS's recommended application method if you use that. It might be useful to do a test mount with AS to find the proper amount to use, ensuring not leaving a grand mess of thermal grease on the cpu and surroundings.


You'll need to run the pump outside the computer while refilling and trying to get rid of inevitable air bubbles. It might also be useful for final cleaning with distilled water, before refilling, in case you don't have a compressor handy. You could avoid getting air in the system by drawing a vacuum through the service valve and letting the vacuum suck the new coolant in. However, that would require some special tools.


Running the pump outside the Quad is also useful as a diagnostic for low coolant/air. The pump is rather noisy when pumping air bubbles.

Oct 5, 2011 1:30 PM in response to Limnos

Speaking of liquid cooled. I've scoured the internet for aquagate NC-1 coolant, and I can't seem to find any in stock. Is there an alternative solution that I could use?


Obviously I don't think I could just use water, as some setups do, and I don't know what kind of concentrations/chemical formulas are specific to the NC-1 that may or may not be necessary.


I don't *THINK* my O-Rings are bad... I mean, I wouldn't know. I'm nearly positive the LCS hasn't leaked, but again, not sure of that either, could always be some internal damage I coudln't see even after taking off the heatsink/CPU cover.


What I don't know is how to measure them. One spec said 1/16" by 1.13" or something like that, but I don't know what those dimensions necessarily refer to. I wish someone *somewhere* would have posted the specs for the Quad's Delphi O-Rings, but it doesn't look like they have... *sigh*


Thus far I've gathered all the tools I needed (they totaled $20... and $20 shipping.. so I've tried reconfigurations and the best I can do is $30 with $5 shipping -_-), and all I need now are O-Rings and coolant!

Oct 5, 2011 10:52 PM in response to Dan-Lempesis-Omega

Why would you especially want NC-1? I'm using Thermochill EC6, clear version, because (1) ready-made liquids are easy and I'm lazy and (2) there won't be any dyes to clog up the system. It seems in some coolants the dyes were/are prone to gunk up the cpu blocks after a while.


If you mix your own, use a corrosion inhibitor, biocide, and distilled water. If you get a premixed coolant, just ensure it's safe for mixed loops. However, I think, a more important parameter than the coolant is regular maintenance of the LCS.


Btw. If you change the O-rings, you'll also probably need silicone grease to lube up the new ones.

Oct 14, 2011 2:00 AM in response to Heikki Lindholm

Ugh. This is sounding more and more complicated the more I hear.


How exactly do I run the LCS out of the case? Could I just disconnect the power to the rest of the components of the computer and simply turn on he machine with the PSU attached to the LCS?


If I buy Thermochill EC6 (found that easily, btw), I won't have to mix it or do anything special.. just pour it straight in? No corrosion inhibitor, biocide etc... right? :/


Any idea what size O-Rings the Quad G5 Delphi system uses?

Oct 14, 2011 8:02 AM in response to Dan-Lempesis-Omega

I posted the pump pinout in another thread. The easiest way is to connect the 12V lines and GND of the pump to a molex connector of a PC ATX power supply. ATX power supplies can be run without the mobo by shorting the green and black leads in the mobo connector.


Thermochill is ready-made. Just pour it straight in.


If your CPU blocks show no apparent signs of leakage don't worry about the O-ring size. They're some red material which google tells me is a sign of them being some silicone compound. The whole CPU block is rather weird-looking. I'll try to post some photos I took of the insides.


If there has been a leak in your system, I'd venture to guess that the prime suspect would the pump, maybe the expansion chamber.

Oct 15, 2011 3:35 AM in response to Heikki Lindholm

Is there any chance you could post it here? Normally I wouldn't ask, but since they've revamped their Discussion layout, the Discussion Forums (every aspect of it..) is dog slow on this computer. Annoying, especially since it used to be perfectly snappy back when this was a regular old 300 MHz G3.


Thanks for the info on the coolant, I'll order that now. As for the ATX PSU... great, I have a few of those lying around =) Although... now that I think about it.. I thought the LCS used proprietary connectors not found on a typical ATX?


Yeah, I've seen the layout of the CPU block.. it's odd.

Oct 16, 2011 10:20 AM in response to Dan-Lempesis-Omega

I ran into trouble with my project. Just before refilling, I noticed that one of the original tubes was deteriorated/cracking at the end that's on the radiator barb. Naturally, it was the pump outlet, i.e. in the hottest place. So, I'll have to source some new tubing. The original tubing, however, is moulded to shape. A straight piece of similar hose would kink at the angles that are used there. I'm now pondering whether I should reroute the tubing in series, like it's in the Dual 2.5 G5s.


The ATX->pump connection can be done with alligator clips and a (broken) male molex lead (I took one from a broken old 486 cpu cooler/fan).


Fwiw, my cpu blocks, or anywhere else for that matter, had very little build-up in them, and opening them now in retrospect seems mostly unnecessary. Of course, you'll never know for sure if you don't open them. The cooling fluid, on the other hand, "sedimented" heavily when left still in a container, and it was full of small floating particles.

Quad G5 Liquid Cooling System overhaul help

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