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 Patrick 01,

    Patrick 01 Patrick 01 Feb 11, 2013 10:05 PM in response to romko23
    Level 1 (80 points)
    Feb 11, 2013 10:05 PM in response to romko23

    romko23 wrote:

     

    I read somewhere, can't remember the website that the single pump came out in April 2006 up until the end of the Quad's run which was August 2006. The dual pump LCS was the first I believe. I will have to research it a bit more.

     

    I'm keeping my dual unit and sorting out it's issues

    Sp lease let me know if you have any advice on the dual

    Thanks

  • by Chris323i,

    Chris323i Chris323i Feb 11, 2013 10:33 PM in response to Patrick 01
    Level 1 (0 points)
    Feb 11, 2013 10:33 PM in response to Patrick 01

    I did actually replace the flexible hosing bits on the underside with the clear tubing I used everywhere else. This was unavoidable though since I had to essentially destroy the old flexible bits to remove them. The adhesive was too strong to prevent me from destroying. I believe they used this different type of tubing to reduce the pressure that the copper blocks would place on the processors when the LCS was mounted. I haven't had any issue with the system since its overhaul. I tried to match Apple's decision on all their sealing and capping all ports and hoses.

    I do have a fuel switch for both closed loop systems that will allow me to reintroduce more coolant if need be. I believe both systems need a tad bit more coolant but I have not gotten around to adding more since the computer runs fine even under heavy load. I should have ran the pumps for a longer period of time before sealing the system up in order to get an accurat liquid observation. When I closed the system up, I believe there was still a bit of lingering air in the system that I was not able to see.

    I too had one CPU running warmer than the other. The upper CPU was lower in coolant, I believe, when I removed the system. As far as what may be causing a higher temp., the #1 concern is low coolant, in a far second is debris/gunk clogging the system.

  • by Patrick 01,

    Patrick 01 Patrick 01 Feb 12, 2013 12:14 AM in response to Chris323i
    Level 1 (80 points)
    Feb 12, 2013 12:14 AM in response to Chris323i

    Chris323i

    Thanks for the information

    I'm going to give this some more thought

    With full load at  highest performance cpu temps are 49,49,60,64

    At reduced mode they are 38, 37,42, 42

    So it may not be a real issue just yet

     

    Either way a coolant change is due.

    Don't think its low as I cant here any swooshing around

  • by G5Lover,

    G5Lover G5Lover May 13, 2013 11:15 AM in response to romko23
    Level 1 (0 points)
    May 13, 2013 11:15 AM in response to romko23

    romko23 wrote:

     

    Sorry to chime in, but is your LCS the dual or single version? The single is by far the more reliable one and it might just be to your advantage to replace the dual with the single pump.. Those came with the later 2006 G5 Quads between April and August of 2006.

    You would be backwards on those facts.

     

    The duel pump units came out AFTER the single pump units. The duel pump units were deemed to be far more  reliable than the single pumps.

  • by G5Lover,

    G5Lover G5Lover May 13, 2013 1:48 PM in response to Patrick 01
    Level 1 (0 points)
    May 13, 2013 1:48 PM in response to Patrick 01

    Patrick 01 wrote:

     

     

    Either way a coolant change is due.

    Don't think its low as I cant here any swooshing around

    On your duel pump LCS system, you won't  hear swooshing sound when the coolant becomes low. This is because the pumps have a VC (volume compensation) feature that compensates for changes in coolant volume. The temperature and fan speeds will be your only indication of low coolant. Keep a close eye on them. Download iStat Pro widget if you don't already have it. That way you can monitor temps, fan and pump speeds.

     

    G5Lover

  • by Ramón G Castañeda,

    Ramón G Castañeda Ramón G Castañeda May 13, 2013 2:09 PM in response to G5Lover
    Level 4 (1,468 points)
    Desktops
    May 13, 2013 2:09 PM in response to G5Lover

    G5Lover wrote:

     

    …On your duel pump LCS system, you won't  hear swooshing sound when the coolant becomes low… The temperature and fan speeds will be your only indication of low coolant… you can monitor temps, fan and pump speeds…

     

    Are there any suggested safe ranges for that?

     

    Here are the values I show at this precise moment, with the weather report showing 90ºF:

     

    Picture 4.png

     

    Compared to last year at the end of April, at a time when outdoors temperature was probably around 75ºF or less:

     

    Hdware_Mon_2012_04_30.png

  • by G5Lover,

    G5Lover G5Lover May 13, 2013 2:40 PM in response to Ramón G Castañeda
    Level 1 (0 points)
    May 13, 2013 2:40 PM in response to Ramón G Castañeda

    For the current ambient temp of 90º F. Those core temps don't appear to be abnormal at all. Only going on what I've read, under no load at normal ambient temp. the cores should be in the high 20s c to low 30s c. Your temps look ok and your fan speeds seem normal for 90º ambient.

     

    My G5 Quad duel LCS pump however started ramping up it's fans about six months ago. The temps are not bad yet but the fans are getting quite noisy keeping it cool. It's definately time to do a flush & refill. The B cores are running about 30º warmer than the A cores (which seem normal). At 70º anbient temp, the B cores are running about 45º C which is warmer than normal. My guess is I'm running low on coolant.

     

    I bought the machine used from a reputable dealer in the beginning of 2011. It's been a great machine up untill it got noisy 6 mo ago. I'm stocking up on supplies and parts right now.

  • by Ramón G Castañeda,

    Ramón G Castañeda Ramón G Castañeda May 13, 2013 2:56 PM in response to G5Lover
    Level 4 (1,468 points)
    Desktops
    May 13, 2013 2:56 PM in response to G5Lover

    Thanks.

     

    What is giving me pause is the pump speed:  2277 RPM vs 1250 RPM

  • by G5Lover,

    G5Lover G5Lover May 13, 2013 3:16 PM in response to Ramón G Castañeda
    Level 1 (0 points)
    May 13, 2013 3:16 PM in response to Ramón G Castañeda

    Pump speed also seems normal for that ambient temp. As long as your temps are staying good, I wouldn't sweat the pump speed. Temps good means everything is working as it should. No worries.

  • by Ramón G Castañeda,

    Ramón G Castañeda Ramón G Castañeda May 13, 2013 4:35 PM in response to G5Lover
    Level 4 (1,468 points)
    Desktops
    May 13, 2013 4:35 PM in response to G5Lover

    Thank you for your reply.  Very comforting. 

  • by G5Lover,

    G5Lover G5Lover May 14, 2013 6:11 PM in response to Chris323i
    Level 1 (0 points)
    May 14, 2013 6:11 PM in response to Chris323i

    Chris,

     

    I'd be interested to know how your system is working since your recent rebuild. Also how the clear Tygon tubing has faired. Curious if the tubing is starting to cloud or not. I also ordered the plasticizer free Tygon tubing but it has some nylon reinforcement in it and I believe a little stiffer than the type you used. I have the exact same quad system with the duel pumps. I'm collecting my supplies to start flushing the system in the next couple weeks.

     

    BTW, thanks for posting those pics. Very helpfull since there are no other examples out there of a quad duel pump rebuild!

     

    G5Lover

  • by BMaverick,

    BMaverick BMaverick May 15, 2013 3:23 PM in response to Heikki Lindholm
    Level 1 (10 points)
    May 15, 2013 3:23 PM in response to Heikki Lindholm

    Just recently, Sean has taken a Laing DDC-1T without VC and merged it with a VC component of the original LCS design for a Quad.  For a few weeks now, no performance issues and no leaks.

     

    My pumps I offer all have the 4-wires and PWM for the G5.  All of the pumps are "new" never used with the 50,000+ run life fully intact.  So, if you are needing a spare pump or some other minor hardware, I have a weird arrary of spare G5 stuff not used.   http://bmaverickddcpumps.wordpress.com/g5-spare-parts

     

    As the G5 LCS ages, the run life of the coolant and the pumps will degrade over time.  And this does not matter the amount of usage nor run hours of the G5.  Even sitting idle ages the coolant corrosion inhibitors. 


    I have an email out to Sean to provide a step-by-step way he converted the pump easily from a DDC-1T to a DDC-1T-VC.

     

    Hope to help others with the G5 LCS systems since these are rare but highly useful workstations even today.

  • by G5Lover,

    G5Lover G5Lover May 15, 2013 6:54 PM in response to BMaverick
    Level 1 (0 points)
    May 15, 2013 6:54 PM in response to BMaverick

    BMav,

     

    Wanted to thank you for all the advise you freely gave me and the new DDC-1T pumps for my quad. My original pumps are operating fine so when I do the flush and fill on my system, I probably won't need to replace the pumps. However I'm glad I have new ones for the future just in case.

     

    A note to anyone else out there planning on rebuilding their LCS. BMaverick still has a limited supply of original new pumps that will work in the G5. If you think you may need a pump(s) in the future, you should order NOW before they are all gone!

     

    Art (AKA) G5Lover

  • by Ramón G Castañeda,

    Ramón G Castañeda Ramón G Castañeda May 15, 2013 7:07 PM in response to G5Lover
    Level 4 (1,468 points)
    Desktops
    May 15, 2013 7:07 PM in response to G5Lover

    If anybody has information on an outfit or technician in the USA that can reliably do this kind of work on the pumps (replacing them, flushing and refilling them, etc) for those of us who don't have the wherewithal to do it ourselves, it would be great and much appreciated if you would share that here. 

     

    I know there's a company in Germany that will do this, but it would be wonderful if it could be done domestically without having to ship the computer overseas.

  • by romko23,

    romko23 romko23 May 15, 2013 8:41 PM in response to G5Lover
    Level 2 (395 points)
    May 15, 2013 8:41 PM in response to G5Lover

    Oh I meant to add.. My serial number on my Single pump G5 is from August 2006, so I would challenge your argument as several techs I have consulted with told me the singles are more reliable than the dual.. But to each their own.. so long as each one's G5 is working, eh?

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