Working on the G5 quad liquid cooling system

Question

Working on the G5 quad liquid cooling system

I have a G5 quad with the one pump Delphi LCS ("version 1"). I'm guessing the LCS is clogged because when the machine sits idle (even in reduced CPU setting, which cuts the GHz in half), the fans and the pump slowly, over several hours, go to full speed. Temperatures of CPU B, particularly the second core, shoot to near 100C when loading the CPUs. ASD 2.6.3 usually passes, but sometimes ends in checkstop and overtemp. A local mac service center, which I had the machine checked at (in hopes of getting free repairs because of a leak), said it's fine.

As a simple first measure, I tried replacing the thermal paste on the CPUs, with little effect. The LCS didn't seem to be leaking or corroded anywhere, but when handling it, it sometimes made a bubbling noise, so, there's probably air in there. I thought I'd take the LCS apart next, but before that I have some questions which I hope someone can answer.

Which one, the upper or lower, is CPU A and which is B? I've read the machine runs on one CPU just fine, but which one?

If I switch the CPUs the other way around and later switch back, does something in the nvram reset so that thermal calibration needs to be run? I'd rather not run it as it seems to have mixed success.

What material/size are the CPU block O-rings on this system?

If I use a vacuum pump on the service valve (I gather it's of the "r134a high" type(?)), what would be a safe level of vacuum? Has anyone tried using the manual brake kits, or car cooling system refill kits that use compressed air and venturi valves, on the LCS?

I suppose I'm just going to try attaching a hose as a reservoir to the service valve and fill through that first, but if that doesn't bring satisfactory results, I'll level-up to some sort of vacuum method.

PowerMac

Posted on Sep 17, 2011 11:59 PM

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Answer 1

Sep 18, 2011 12:45 AM in response to Heikki Lindholm

I'll be following this thread with great interest given the uncertainty that reigns throughout the net as to the true nature of the pumps.

On a recent thread, romko23 seemed to think that the double pumps meant Delphi and the single pump meant Panasonic. There's not much on the net to show which one is which, and which of the two cooling systems, dual pumps vs. single pump, is the most desirable.

https://discussions.apple.com/thread/3232389?start=0&tstart=0

There has been also contradiuctory advice as the the wisdom of re-doing the thermal paste and of flushung the cooling system. A tech that used to work for Apple (in manufacturing) recently expressed a firm opinion that flushing the system should only be a measure of last resort, when there is no alternative other than discarding the LCS as a whole. It was also his contention that Apple reverted to the Delphi pumps because the Panasonics "did not hold up as long as it had been hoped". The credibility of this particular independent technician tends to be bolstered by the excellent quality of his work but downgraded by his, um, ethical deficit in dealing with customers' credit card information. (That's a whole 'nother, ugly story.)

EDIT: Sorry, I had to correct the link, as the one I inserted initially led to the wrong thread. It is now corrected.

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Answer 2

japamac

Level 7

24,400 points

Sep 18, 2011 12:43 AM in response to Heikki Lindholm

Hi-

The upper is CPU A.

If you switch CPUs, you need to thermal calibrate with the ASD 2.6.3.

Invaluable reading:

http://www.xlr8yourmac.com/systems/G5_CoolantLeak_Repair/G5_CoolantLeak_Repair.h tml

http://www.xlr8yourmac.com/systems/G5_coolant_leaks.html

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Answer 3

Sep 18, 2011 12:47 AM in response to Ramón G Castañeda

https://discussions.apple.com/thread/3232389?start=0&tstart=0

EDIT: Sorry, I had to correct the link, as the one I inserted initially led to the wrong thread. It is now corrected.

Please note that I edited my previous post, which will not be obvious to those accessing this forum via emal. My bad.

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Answer 4

Sep 18, 2011 1:38 AM in response to Ramón G Castañeda

As far as I can tell, and according to the service manual, there are two versions of the quad G5 LCS: version 1, which is made by Delphi and has one pump, and version 2, which is made by Cooligy and has two pumps. I've never seen a Panasonic cooling system mentioned in relation to the quad G5, but I've no inside track on these things.

In any cooling system that has rubber hoses, the liquid will evaporate to a degree. Also, the dyes in the coolants and the plasticizers leaching from the hoses eventually can clog up the system. So, I have great reservations about claims that the LCS in G5 would be service free for a much larger extent than water cooling rigs built by pc enthusiasts, which might work for a year or two without service.

From design point of view the quad G5 LCS does seem somewhat better than the Delphi system in the dual 2.5 GHz Mac as, from what I can see, the pump draws its suction from the bottom of the radiator, which is sure to have liquid even if some has evaporated.

In my opinion, the version 1 LCS seems vastly more desirable simply because it's much easier to service. It can be taken apart and rebuilt without having to break or glue anything or replace any parts. Also, the cpu cooling blocks can be serviced more easily (O-rings changed, cleaned up) in the version 1 system.

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Answer 5

Sep 18, 2011 1:33 AM in response to japamac

japamac:

Thanks for the answer. As I understand, if I switch the CPUs and don't do a thermal calibration, the system will work, but with fans full blast - haven't tried it yet, though. However, I'd just like to switch them for the sake of testing whether the "hot cpu" is more caused by the cpu than the cooling system or not. At that point I don't care about the fans, I'm running them full blast anyway to make a reasonable setup for measuring the CPU temps.

Anyway, my point in asking was that if I later change the CPUs back to how they originally were, and never do a thermal calibration, does the system still think it needs a calibration and sets fans full blast?

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Answer 6

Sep 18, 2011 1:46 AM in response to Heikki Lindholm

Heikki Lindholm wrote:

As far as I can tell, and according to the service manual, there are two versions of the quad G5 LCS: version 1, which is made by Delphi and has one pump, and version 2, which is made by Cooligy and has two pumps. I've never seen a Panasonic cooling system mentioned in relation to the quad G5, but I've no inside track on these things…

I have no inside track either and had also not read any mention of Panasonic in this regard. It was forum user romko23 who brought up the Panasonic name first, and the ethically challenged tech I mentioned seemed to run with it quite naturally. He seemed very knowledgeable and friendly, other than his penchant for making fraudulent charges to a customer's credit card within a few minutes of having gotten a hold of the information. 😠

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Answer 7

Sep 18, 2011 2:03 AM in response to Ramón G Castañeda

I have no inside track either and had also not read any mention of Panasonic in this regard. It was forum user romko23 who brought up the Panasonic name first, and the ethically challenged tech I

Maybe he was talking about the dual G5 not the quad. The late 2004 service manual does mention a Panasonic cooling system.

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Answer 8

Sep 18, 2011 2:14 AM in response to Heikki Lindholm

Heikki Lindholm wrote:

…Maybe he was talking about the dual G5 not the quad. The late 2004 service manual does mention a Panasonic cooling system.

We were definitely discussing the Quad, specifically mine which was built in late June of 2006, but he may have been mistaken about the Panasonic in the Quad.

Thanks for that very helpful clarification.

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Answer 9

Sep 18, 2011 2:20 AM in response to Heikki Lindholm

Perhaps you can identify one or both types in this image that was mentioned in the discussion?

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Answer 10

Sep 18, 2011 2:28 AM in response to Heikki Lindholm

My apologies. The link in my first reply still links to the wrong discussion.

The thread where the controversy of dual vs. single pumps arose is this one:

https://discussions.apple.com/thread/3232389?start=0&tstart=0

My bad.

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Answer 11

Sep 18, 2011 2:31 AM in response to Ramón G Castañeda

The contestant on the left would be the Delphi system, aka version 1, and the contestant on the right is the Cooligy one, aka version 2.

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Answer 12

Sep 18, 2011 2:39 AM in response to Heikki Lindholm

That is most helpful. Thank you so much!

Hope romko23 drops by, he really should appreciate this. 🙂

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Answer 13

japamac

Level 7

24,400 points

Sep 18, 2011 5:23 AM in response to Heikki Lindholm

if I switch the CPUs and don't do a thermal calibration, the system will work, but with fans full blast

That is the case.

I'd just like to switch them for the sake of testing whether the "hot cpu" is more caused by the cpu than the cooling system or not.

Switching CPU positions is a very good troubleshooting technique.

if I later change the CPUs back to how they originally were, and never do a thermal calibration, does the system still think it needs a calibration and sets fans full blast?

The system should "think" that all is normal if all is as originally installed.

The majority of cases don't need calibration, though many do it to be thorough.

Also, the use of the ASD disc sometimes "cures" cases of "gremlins in the system"; strange oddities which are hard to pin point yet occur.....

Should you desire a copy of 2.6.3, send me an email via my website listed in my profile.

I can help get you a good copy.

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Answer 14

Sep 19, 2011 9:14 AM in response to japamac

Indeed the system seems to run fine with one CPU card (the top one). With CPU B in the CPU A slot, still a single CPU card setup, it also works fine, and doesn't actually set the fans to full tilt. No calibrations necessary. In my case, CPU B actually worked cooler in the A slot than the original CPU A, so the cooling system is definitely at fault.

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Answer 15

romko23

Level 2

408 points

Sep 19, 2011 4:37 PM in response to Ramón G Castañeda

Hi,

Ok, so the single pumps that you and I have are by Delphi. Great! But unless someone can get a real close up of the version 1 LCS and identify it by name of Panasonic or even Delphi, I will put it as a question mark. I have taken my G5 off line due to some messages I read regarding about a DigiNotar ROOT CA certificate and the fact that we are no longer getting software security updates anymore, which put us PowerPC users at high risk for our information to be stolen. Evidentally, Apple does not want us using the PPC macs.. Unless someone can really REALLY translate what all this means from www.lowendmac.com, I have decided to keep my G5 off line until further notice as I don't want someone to steal my information and use it against me.

I am clueless when it comes to the single pump though, as it seems like it was only added in the mid to end cycle of the G5 Quad.. figure around April to August of 2006.

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