Heikki Lindholm

Q: 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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Q: Working on the G5 quad liquid cooling system

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  • by BDAqua,

    BDAqua BDAqua Nov 2, 2011 1:58 PM in response to Heikki Lindholm
    Level 10 (123,765 points)
    Nov 2, 2011 1:58 PM in response to Heikki Lindholm

    Nice work, thanks

  • by BMaverick,

    BMaverick BMaverick Nov 10, 2011 1:07 PM in response to zampanone
    Level 1 (10 points)
    Nov 10, 2011 1:07 PM in response to zampanone

    Let's keep this LCS thing simple.  Seems that people are getting the wrong LCS makers confused in postings/replys.

     

    1-pump Laing DDC LCS = Delphi

     

    2-pumps Laing DDC LCS = CoolIT

     

    2-pumps; one each atop water-blocks LCS = Panasonic

  • by subsidence,

    subsidence subsidence Jan 17, 2012 8:45 PM in response to Heikki Lindholm
    Level 1 (0 points)
    Jan 17, 2012 8:45 PM in response to Heikki Lindholm

    Silcone is an excelent material for the LCR. Delphi has been making liquid coolers for 75 years. Half of us on this thread most likely have Delphi parts in our cars Domestic or Foreign. The issue is so simple though. Placing a chamber of liquid directly above delicate electronics is a recipe for fails.

     

    What I think really went wrong in these O-Rings is that it wasnt so much physical liquid leaking out..It was rather slow evaporation and vapors that seep through the o-ring while under high CPU heat loads, this then eats away at the heat plates and CPU. Yes Im sure many fails have happened from o-ring cracks and tube leaks..those being the extreme. I have my Dual 2.5 G5 running good. I check it from time to time and also frequent these cooling threads to keep on the finds of DYIers in the need I have to overhaul it. ATM I see no need too as my inspections come back good.

     

    FWIW..Go with Viton material its wonderful when used with glycol and other presurized heated lliquids. In fact i might be overkill..lol

  • by BMaverick,

    BMaverick BMaverick Jan 18, 2012 5:41 AM in response to subsidence
    Level 1 (10 points)
    Jan 18, 2012 5:41 AM in response to subsidence

    Silcone is a good material.  However, I would not allow the silicone to cure around any electrical components or contacts within 30 feet.  And even then allow the cure process to take two weeks to ensure the cure shape took hold. 

     

    Silicone contamination of electrical switch contacts can lead to failures by causing an increase in contact resistance, often late in the life of the contact, well after any testing is completed when the product is in the consumers hand.  All that is requied is a silicone spray or silicone to cure around these contacts.

     

    How many contacts in a basic computer .... hundreds !

     

    Contacts are CPU to MB, graphics card to MB, the main power switch, the connections to each hard drive, the USB port and any port on the computer, etc .... 

     

    Also, I would agree Delphi (GM Harrison Radiator, ACG) has been making cooling products for nearly a century.  However, like any company, they too have had recalls, quality spills, and liability blunders.

  • by Chris323i,

    Chris323i Chris323i Jan 22, 2012 10:42 PM in response to Heikki Lindholm
    Level 1 (0 points)
    Jan 22, 2012 10:42 PM in response to Heikki Lindholm

    Wow, thank you for this detailed write-up! I will be using your information as a valuable reference.

    I just purchased a used Quadcore G5 with dual Delphi cooling units and this issue hit me at complete surprise as I thought leaking was the only issue revolving around Powermacs. Consequently, leaking was the only thing I checked for during before my purchase of the machine. During my last successful boot-up I managed to download iStat Pro and I carefully watched as CPU B temperature reached 80*C before the computer shut itself down. CPU A only reached ~50*C max during that last operation, which lasted about 10-15 minutes total. The fans seemed to stay at about a medium speed from boot-up until shut down. Any attempts to start the Powermac after a successful boot results in an expected hang-up after the chime and the two signature red LEDs activated inside the Powermac. The Powermac must be at ambient room temperature to boot successfully. Interestingly enough, the previous owner had been running the machine with no problems or excessive fan speed. I have been thinking that something in the pumps or radiator must have been dislodged when I layed the Powermac on its side when transporting it to my house.

    Anyhow, I will be attempting this cleanup of the internals when I get a chance. Thanks again!

  • by Chris323i,

    Chris323i Chris323i Jan 22, 2012 11:15 PM in response to Heikki Lindholm
    Level 1 (0 points)
    Jan 22, 2012 11:15 PM in response to Heikki Lindholm

    Also, Heikki and those knowledgable on the subject, I was curious to find out what opinions are on replacing the Delphi pumps themselves during this whole process instead of cleaning them out? Would this create compatibility issues when running calibration from ASD disk since the pumps are not Delphi?

    I have come across this product on another forum as a possible replacement for the Delphi units. http://www.svc.com/mcp355.html

  • by Chris323i,

    Chris323i Chris323i Jan 22, 2012 11:25 PM in response to Chris323i
    Level 1 (0 points)
    Jan 22, 2012 11:25 PM in response to Chris323i

    Judging by the specifications for the Delphi MCP355 pumps listed here: http://www.sidewindercomputers.com/swiftechmcp355.html I am reading that the mean time between failures is listed as 5 years. This is almost reason enough to replace them both as the units are now over 6 years old. This is taking into account those that like to leave their Quad cores on for most of the machine's lifetime.

  • by Heikki Lindholm,

    Heikki Lindholm Heikki Lindholm Jan 22, 2012 11:35 PM in response to Chris323i
    Level 1 (135 points)
    Jan 22, 2012 11:35 PM in response to Chris323i

    Chris, I've been meaning to update my writeup on the subject of pumps. Apple used Laing (Delphi branded) DDC-1 pumps in the Dual G5 LCS, and DDC-2 and DDC-3.2 pumps in the Quad G5 LCS. The Swiftech MCP350 and MCP355 were these same Laing models, rebranded. From past discussions here you might be fooled to think that you can just go to a PC store and get a Swiftech or a Laing to replace the pump(s). However, that's not the case anymore. Laing changed the electronics in the pump and all the current models, sold as Laing DDC-1T/1Tplus and Swiftech MCP350/355, are incompatible with the Power Mac G5 signalling.

     

    My advice is to be VERY CAREFUL with the pumps. Applying voltage to a wrong pin will destroy the pump, and finding a replacement will be difficult.

     

    That said, the best replacement for the Quad G5 pumps is the DDC-3.2, which can be identified from a "3.3" sticker on the PCB of the pump. The DDC-2 pumps are also compatible, but they're notorious for breaking down; they were too powerful or something. For the Dual G5 machines, bmaverick has a hoard of DDC-1 pumps that are compatible with the Dual G5 pump control, and his pumps are new. Finding DDC-2 or DDC-3.2 pumps unused seems very unlikely.

     

    You actually can use the newer pumps with the Quad G5, but you will lose the motor control, which in practice means the pump will run slightly louder than the fans. AFAIK, the Dual G5s can't even read the tacho/rpm signal of the newer pumps.

  • by Heikki Lindholm,

    Heikki Lindholm Heikki Lindholm Jan 23, 2012 12:21 AM in response to Chris323i
    Level 1 (135 points)
    Jan 23, 2012 12:21 AM in response to Chris323i

    One additional note. The "3.3" PCB pumps can also be identified by looking at the wires coming out of the pump. The wires should be black, yellow, blue, in that order, for the correct version of the pump. Trouble the dealer to check this before buying. With some luck, some dealers still have old stock of the DDC-3.2 pumps.

    (See http://www.techpowerup.com/forums/showthread.php?t=72085 for picture of a compatible pump PCB)

     

    Good luck with the project!

  • by Chris323i,

    Chris323i Chris323i Jan 24, 2012 9:32 AM in response to Chris323i
    Level 1 (0 points)
    Jan 24, 2012 9:32 AM in response to Chris323i

    Just to note the difference between the arrangements. Hosing is reduced in the Quad core by a significant amount. I will be cleaning out the pumps and radiator within the net few weeks and I will be updating everyone on any performance improvements.

     

    /___sbsstatic___/migration-images/173/17388778-1.jpg

  • by Ramón G Castañeda,

    Ramón G Castañeda Ramón G Castañeda Jan 24, 2012 9:56 AM in response to Chris323i
    Level 4 (1,468 points)
    Desktops
    Jan 24, 2012 9:56 AM in response to Chris323i

    Chris323i wrote:

     

    Just to note the difference between the arrangements. Hosing is reduced in the Quad core by a significant amount…

     

    /___sbsstatic___/migration-images/173/17388994-1.jpg

     

    That's a most illustrative and helpful picture, thank you—especially from those of us who have been just too chicken to take our Quads apart.  (Hope your thumb is OK now.  )

     


    Chris323i wrote:

     

    …and I will be updating everyone on any performance improvements…

     

    Duly and truly appreciated.  

  • by subsidence,

    subsidence subsidence Jan 25, 2012 4:49 PM in response to Heikki Lindholm
    Level 1 (0 points)
    Jan 25, 2012 4:49 PM in response to Heikki Lindholm

    BTW. Anyone having luck recalibrating the fans?

  • by BDAqua,

    BDAqua BDAqua Jan 25, 2012 8:00 PM in response to subsidence
    Level 10 (123,765 points)
    Jan 25, 2012 8:00 PM in response to subsidence

    Have you tried the ASD for your G5,either 2.5.8 or 2.6.3?

  • by Chris323i,

    Chris323i Chris323i Jan 25, 2012 8:19 PM in response to Ramón G Castañeda
    Level 1 (0 points)
    Jan 25, 2012 8:19 PM in response to Ramón G Castañeda

    Here are a few extra pictures I managed to grab during the teardown.

     

    This photo was taken showing both processor boards attached to the cooling system.

    /___sbsstatic___/migration-images/174/17404533-1.jpg

     

     

    Here you can see how large of a difference this plumbing system varies from the dual core setup.

    /___sbsstatic___/migration-images/174/17404533-2.jpg

     

     

    Here I was taking a picture of the unique tubing that is located on each side of the copper blocks. This plastic material seems much weaker than the thick tubing located near the radiator. Also note the extra sealer. It can be found at every hose attachment point.

    /___sbsstatic___/migration-images/174/17404533-3.jpg

  • by Heikki Lindholm,

    Heikki Lindholm Heikki Lindholm Jan 25, 2012 9:09 PM in response to Chris323i
    Level 1 (135 points)
    Jan 25, 2012 9:09 PM in response to Chris323i

    Just to make sure the confusion doesn't arise again: these pictures are from a "version 2" of the Quad G5 LCS (mine was "version 1", which in turn is a 2nd generation Delphi unit). IMHO, they really went overboard on the version 2 epoxying even the pump connections. The barbed connections in combination with the rubber hose are already very tight and very unlikely to leak even without the clamps, let alone the epoxy.

     

    Chris, could you take a close-up of the pumps' power connection, so that the jumpering on the pumps' side of the connection is visible? The jumper, as far as i can understand, decides which LCS version (i.e. how many pumps) the motherboard thinks there is.

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